fix: cannot auto unlink payments for credit/debit notes (#23689)

diff --git a/erpnext/controllers/accounts_controller.py b/erpnext/controllers/accounts_controller.py
index 1665649..1818cb6 100644
--- a/erpnext/controllers/accounts_controller.py
+++ b/erpnext/controllers/accounts_controller.py
@@ -605,8 +605,6 @@
 		from erpnext.accounts.utils import unlink_ref_doc_from_payment_entries
 
 		if self.doctype in ["Sales Invoice", "Purchase Invoice"]:
-			if self.is_return: return
-
 			if frappe.db.get_single_value('Accounts Settings', 'unlink_payment_on_cancellation_of_invoice'):
 				unlink_ref_doc_from_payment_entries(self)