chore: clean up purchase invoice and purchase invoice item

1. remove discount accounting related fields from purchase invoice and
purchase invoice item
2. clean buying settings doctype
diff --git a/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.json b/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.json
index 986fc03..3020e6d 100644
--- a/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.json
+++ b/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.json
@@ -98,7 +98,6 @@
   "section_break_44",
   "apply_discount_on",
   "base_discount_amount",
-  "additional_discount_account",
   "column_break_46",
   "additional_discount_percentage",
   "discount_amount",
@@ -1388,12 +1387,6 @@
    "read_only": 1
   },
   {
-   "fieldname": "additional_discount_account",
-   "fieldtype": "Link",
-   "label": "Additional Discount Account",
-   "options": "Account"
-  },
-  {
    "default": "0",
    "fieldname": "ignore_default_payment_terms_template",
    "fieldtype": "Check",
@@ -1445,7 +1438,7 @@
  "idx": 204,
  "is_submittable": 1,
  "links": [],
- "modified": "2022-09-13 23:39:54.525037",
+ "modified": "2022-09-27 11:07:55.766844",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Purchase Invoice",
diff --git a/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py b/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py
index d185300..2b633cb 100644
--- a/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py
+++ b/erpnext/accounts/doctype/purchase_invoice/purchase_invoice.py
@@ -669,9 +669,6 @@
 
 		exchange_rate_map, net_rate_map = get_purchase_document_details(self)
 
-		enable_discount_accounting = cint(
-			frappe.db.get_single_value("Buying Settings", "enable_discount_accounting")
-		)
 		provisional_accounting_for_non_stock_items = cint(
 			frappe.db.get_value(
 				"Company", self.company, "enable_provisional_accounting_for_non_stock_items"
@@ -1159,9 +1156,6 @@
 	def make_tax_gl_entries(self, gl_entries):
 		# tax table gl entries
 		valuation_tax = {}
-		enable_discount_accounting = cint(
-			frappe.db.get_single_value("Buying Settings", "enable_discount_accounting")
-		)
 
 		for tax in self.get("taxes"):
 			amount, base_amount = self.get_tax_amounts(tax, None)
@@ -1249,15 +1243,6 @@
 						)
 					)
 
-	@property
-	def enable_discount_accounting(self):
-		if not hasattr(self, "_enable_discount_accounting"):
-			self._enable_discount_accounting = cint(
-				frappe.db.get_single_value("Buying Settings", "enable_discount_accounting")
-			)
-
-		return self._enable_discount_accounting
-
 	def make_internal_transfer_gl_entries(self, gl_entries):
 		if self.is_internal_transfer() and flt(self.base_total_taxes_and_charges):
 			account_currency = get_account_currency(self.unrealized_profit_loss_account)
diff --git a/erpnext/accounts/doctype/purchase_invoice_item/purchase_invoice_item.json b/erpnext/accounts/doctype/purchase_invoice_item/purchase_invoice_item.json
index 7fa2fe2..fca7e3a 100644
--- a/erpnext/accounts/doctype/purchase_invoice_item/purchase_invoice_item.json
+++ b/erpnext/accounts/doctype/purchase_invoice_item/purchase_invoice_item.json
@@ -74,7 +74,6 @@
   "manufacturer_part_no",
   "accounting",
   "expense_account",
-  "discount_account",
   "col_break5",
   "is_fixed_asset",
   "asset_location",
@@ -861,12 +860,6 @@
    "read_only": 1
   },
   {
-   "fieldname": "discount_account",
-   "fieldtype": "Link",
-   "label": "Discount Account",
-   "options": "Account"
-  },
-  {
    "fieldname": "product_bundle",
    "fieldtype": "Link",
    "label": "Product Bundle",
@@ -877,7 +870,7 @@
  "idx": 1,
  "istable": 1,
  "links": [],
- "modified": "2022-06-17 05:31:10.520171",
+ "modified": "2022-09-27 10:54:23.980713",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Purchase Invoice Item",
diff --git a/erpnext/buying/doctype/buying_settings/buying_settings.json b/erpnext/buying/doctype/buying_settings/buying_settings.json
index aad2607..28158a3 100644
--- a/erpnext/buying/doctype/buying_settings/buying_settings.json
+++ b/erpnext/buying/doctype/buying_settings/buying_settings.json
@@ -20,7 +20,6 @@
   "maintain_same_rate",
   "allow_multiple_items",
   "bill_for_rejected_quantity_in_purchase_invoice",
-  "enable_discount_accounting",
   "subcontract",
   "backflush_raw_materials_of_subcontract_based_on",
   "column_break_11",
@@ -134,13 +133,6 @@
   {
    "fieldname": "column_break_12",
    "fieldtype": "Column Break"
-  },
-  {
-   "default": "0",
-   "description": "If enabled, additional ledger entries will be made for discounts in a separate Discount Account",
-   "fieldname": "enable_discount_accounting",
-   "fieldtype": "Check",
-   "label": "Enable Discount Accounting for Buying"
   }
  ],
  "icon": "fa fa-cog",
@@ -148,7 +140,7 @@
  "index_web_pages_for_search": 1,
  "issingle": 1,
  "links": [],
- "modified": "2022-09-01 18:01:34.994657",
+ "modified": "2022-09-27 10:50:27.050252",
  "modified_by": "Administrator",
  "module": "Buying",
  "name": "Buying Settings",
diff --git a/erpnext/buying/doctype/buying_settings/buying_settings.py b/erpnext/buying/doctype/buying_settings/buying_settings.py
index 7b18cdb..be1ebde 100644
--- a/erpnext/buying/doctype/buying_settings/buying_settings.py
+++ b/erpnext/buying/doctype/buying_settings/buying_settings.py
@@ -5,15 +5,10 @@
 
 
 import frappe
-from frappe.custom.doctype.property_setter.property_setter import make_property_setter
 from frappe.model.document import Document
-from frappe.utils import cint
 
 
 class BuyingSettings(Document):
-	def on_update(self):
-		self.toggle_discount_accounting_fields()
-
 	def validate(self):
 		for key in ["supplier_group", "supp_master_name", "maintain_same_rate", "buying_price_list"]:
 			frappe.db.set_default(key, self.get(key, ""))
@@ -26,60 +21,3 @@
 			self.get("supp_master_name") == "Naming Series",
 			hide_name_field=False,
 		)
-
-	def toggle_discount_accounting_fields(self):
-		enable_discount_accounting = cint(self.enable_discount_accounting)
-
-		make_property_setter(
-			"Purchase Invoice Item",
-			"discount_account",
-			"hidden",
-			not (enable_discount_accounting),
-			"Check",
-			validate_fields_for_doctype=False,
-		)
-		if enable_discount_accounting:
-			make_property_setter(
-				"Purchase Invoice Item",
-				"discount_account",
-				"mandatory_depends_on",
-				"eval: doc.discount_amount",
-				"Code",
-				validate_fields_for_doctype=False,
-			)
-		else:
-			make_property_setter(
-				"Purchase Invoice Item",
-				"discount_account",
-				"mandatory_depends_on",
-				"",
-				"Code",
-				validate_fields_for_doctype=False,
-			)
-
-		make_property_setter(
-			"Purchase Invoice",
-			"additional_discount_account",
-			"hidden",
-			not (enable_discount_accounting),
-			"Check",
-			validate_fields_for_doctype=False,
-		)
-		if enable_discount_accounting:
-			make_property_setter(
-				"Purchase Invoice",
-				"additional_discount_account",
-				"mandatory_depends_on",
-				"eval: doc.discount_amount",
-				"Code",
-				validate_fields_for_doctype=False,
-			)
-		else:
-			make_property_setter(
-				"Purchase Invoice",
-				"additional_discount_account",
-				"mandatory_depends_on",
-				"",
-				"Code",
-				validate_fields_for_doctype=False,
-			)