Replace frappe.db.sql to frappe.get_list to apply permissions (#14037)

* Replace frappe.db.sql to frappe.get_list to apply permission
- All get_children method had frappe.db.sql in them which
had no permission check, now its replaced with frappe.get_list
which will check permission based on the user.

* Fix codacy
- Remove trailing whitespace

erpnext/agriculture/doctype/land_unit/land_unit.py

@@ -169,11 +169,10 @@ def get_children(doctype, parent, is_root=False):
 	if is_root:
 		parent = ''
 
-	land_units = frappe.db.sql("""select name as value,
-		is_group as expandable
-		from `tabLand Unit`
-		where ifnull(`parent_land_unit`,'') = %s
-		order by name""", (parent), as_dict=1)
+	land_units = frappe.get_list(doctype,
+		fields = ['name as value', 'is_group as expandable'],
+		filters= [['parent_land_unit', '=', parent]],
+		order_by='name')
 
 	# return nodes
 	return land_units