Remove escaped customer string (#13986)

- no need to escape strings that are passed to the values parameter of the sql method
- this query was failing for inputs like "D'Arby" which have quotes
diff --git a/erpnext/selling/doctype/customer/customer.py b/erpnext/selling/doctype/customer/customer.py
index 0ea1119..7232fad 100644
--- a/erpnext/selling/doctype/customer/customer.py
+++ b/erpnext/selling/doctype/customer/customer.py
@@ -316,7 +316,7 @@
 	return address
 
 def get_customer_primary_contact(doctype, txt, searchfield, start, page_len, filters):
-	customer = frappe.db.escape(filters.get('customer'))
+	customer = filters.get('customer')
 	return frappe.db.sql("""
 		select `tabContact`.name from `tabContact`, `tabDynamic Link`
 			where `tabContact`.name = `tabDynamic Link`.parent and `tabDynamic Link`.link_name = %(customer)s