fix: postgres query (#19357)

Double quotes are supposed to be used for table/columns only in
postgres. Mariadb is fine with either.


[skip ci]

frappe/contacts/doctype/contact/contact.py

@@ -141,7 +141,7 @@ def get_default_contact(doctype, name):
 		where
 			dl.link_doctype=%s and
 			dl.link_name=%s and
-			dl.parenttype = "Contact"''',
+			dl.parenttype = 'Contact' ''',
 		(doctype, name),
 		as_dict=True,
 	)