refactor: changed the fieldtype from data to small text (#21782)

diff --git a/erpnext/accounts/doctype/sales_invoice/sales_invoice.json b/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
index db20589..63c34ed 100644
--- a/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
+++ b/erpnext/accounts/doctype/sales_invoice/sales_invoice.json
@@ -398,7 +398,7 @@
   {
    "allow_on_submit": 1,
    "fieldname": "po_no",
-   "fieldtype": "Data",
+   "fieldtype": "Small Text",
    "label": "Customer's Purchase Order",
    "no_copy": 1,
    "print_hide": 1
@@ -1579,7 +1579,7 @@
  "idx": 181,
  "is_submittable": 1,
  "links": [],
- "modified": "2020-04-29 13:37:09.355300",
+ "modified": "2020-05-19 17:00:57.208696",
  "modified_by": "Administrator",
  "module": "Accounts",
  "name": "Sales Invoice",
diff --git a/erpnext/stock/doctype/delivery_note/delivery_note.json b/erpnext/stock/doctype/delivery_note/delivery_note.json
index 9f5dee9..84d2057 100644
--- a/erpnext/stock/doctype/delivery_note/delivery_note.json
+++ b/erpnext/stock/doctype/delivery_note/delivery_note.json
@@ -24,10 +24,10 @@
   "return_against",
   "customer_po_details",
   "po_no",
-  "section_break_18",
-  "pick_list",
   "column_break_17",
   "po_date",
+  "section_break_18",
+  "pick_list",
   "contact_info",
   "shipping_address_name",
   "shipping_address",
@@ -296,7 +296,6 @@
   },
   {
    "collapsible": 1,
-   "collapsible_depends_on": "po_no",
    "fieldname": "customer_po_details",
    "fieldtype": "Section Break",
    "label": "Customer PO Details"
@@ -304,7 +303,7 @@
   {
    "allow_on_submit": 1,
    "fieldname": "po_no",
-   "fieldtype": "Data",
+   "fieldtype": "Small Text",
    "label": "Customer's Purchase Order No",
    "no_copy": 1,
    "oldfieldname": "po_no",
@@ -318,7 +317,6 @@
    "fieldtype": "Column Break"
   },
   {
-   "depends_on": "eval:doc.po_no",
    "fieldname": "po_date",
    "fieldtype": "Date",
    "label": "Customer's Purchase Order Date",
@@ -326,7 +324,6 @@
    "oldfieldtype": "Data",
    "print_hide": 1,
    "print_width": "100px",
-   "read_only": 1,
    "width": "100px"
   },
   {
@@ -1256,7 +1253,7 @@
  "idx": 146,
  "is_submittable": 1,
  "links": [],
- "modified": "2020-04-17 12:51:41.288600",
+ "modified": "2020-05-19 17:03:45.880106",
  "modified_by": "Administrator",
  "module": "Stock",
  "name": "Delivery Note",