fix: order_type validation restriction (#18096)

diff --git a/erpnext/controllers/selling_controller.py b/erpnext/controllers/selling_controller.py
index 9dbd5be..9a9f3d1 100644
--- a/erpnext/controllers/selling_controller.py
+++ b/erpnext/controllers/selling_controller.py
@@ -148,13 +148,6 @@
 		if sales_team and total != 100.0:
 			throw(_("Total allocated percentage for sales team should be 100"))
 
-	def validate_order_type(self):
-		valid_types = ["Sales", "Maintenance", "Shopping Cart"]
-		if not self.order_type:
-			self.order_type = "Sales"
-		elif self.order_type not in valid_types:
-			throw(_("Order Type must be one of {0}").format(comma_or(valid_types)))
-
 	def validate_max_discount(self):
 		for d in self.get("items"):
 			if d.item_code:
diff --git a/erpnext/selling/doctype/quotation/quotation.py b/erpnext/selling/doctype/quotation/quotation.py
index 790b2f0..9ebef0d 100644
--- a/erpnext/selling/doctype/quotation/quotation.py
+++ b/erpnext/selling/doctype/quotation/quotation.py
@@ -26,7 +26,6 @@
 		super(Quotation, self).validate()
 		self.set_status()
 		self.update_opportunity()
-		self.validate_order_type()
 		self.validate_uom_is_integer("stock_uom", "qty")
 		self.validate_valid_till()
 		self.set_customer_name()
@@ -40,9 +39,6 @@
 	def has_sales_order(self):
 		return frappe.db.get_value("Sales Order Item", {"prevdoc_docname": self.name, "docstatus": 1})
 
-	def validate_order_type(self):
-		super(Quotation, self).validate_order_type()
-
 	def update_lead(self):
 		if self.quotation_to == "Lead" and self.party_name:
 			frappe.get_doc("Lead", self.party_name).set_status(update=True)
diff --git a/erpnext/selling/doctype/sales_order/sales_order.py b/erpnext/selling/doctype/sales_order/sales_order.py
index 2112a41..94bbb79 100755
--- a/erpnext/selling/doctype/sales_order/sales_order.py
+++ b/erpnext/selling/doctype/sales_order/sales_order.py
@@ -34,7 +34,6 @@
 
 	def validate(self):
 		super(SalesOrder, self).validate()
-		self.validate_order_type()
 		self.validate_delivery_date()
 		self.validate_proj_cust()
 		self.validate_po()
@@ -100,9 +99,6 @@
 					frappe.msgprint(_("Quotation {0} not of type {1}")
 						.format(d.prevdoc_docname, self.order_type))
 
-	def validate_order_type(self):
-		super(SalesOrder, self).validate_order_type()
-
 	def validate_delivery_date(self):
 		if self.order_type == 'Sales' and not self.skip_delivery_note:
 			delivery_date_list = [d.delivery_date for d in self.get("items") if d.delivery_date]