[16.0][FIX] rma_account: fiscal_position_id is a computed field

In v16, fiscal_position_id is a computed field, so if we set up the field in the refund creation we are overriding the computed value

rma_account/wizards/rma_refund.py

@@ -167,7 +167,6 @@ def _prepare_refund(self, wizard, rma_line):
             "ref": ref,
             "move_type": "in_refund" if rma_line.type == "supplier" else "out_refund",
             "journal_id": journal.id,
-            "fiscal_position_id": rma_line.partner_id.property_account_position_id.id,
             "state": "draft",
             "currency_id": self._get_refund_currency(rma_line).id,
             "date": wizard.date,