[FIX] l10n_ar: get_fiscal_position inheritance

The method get_fiscal_position was missing the @api.model decorator

closes odoo/odoo#58665

X-original-commit: 7cad8db251b62972b3a0ea8ca970014cd0f1b5c1
Signed-off-by: Josse Colpaert <jco@openerp.com>

addons/l10n_ar/models/account_fiscal_position.py

@@ -11,6 +11,7 @@ class AccountFiscalPosition(models.Model):
         string='AFIP Responsibility Types', help='List of AFIP responsibilities where this fiscal position '
         'should be auto-detected')
 
+    @api.model
     def get_fiscal_position(self, partner_id, delivery_id=None):
         """ Take into account the partner afip responsibility in order to auto-detect the fiscal position """
         company = self.env.company