Use only foreign Many2One for domain on field for field access

The Char fields are not filled when using the foreign Many2One so the domain
must rely only on the foreign Many2One.

Closes #14081

trytond/trytond/ir/model.py

@@ -763,7 +763,7 @@ class ModelFieldAccess(
             'field_ref', 'field,model', 'ir.model.field,name,model', "Field",
             required=True, ondelete='CASCADE',
             domain=[
-                ('model', '=', Eval('model')),
+                ('model_ref', '=', Eval('model_ref', -1)),
                 ]),
         DeactivableMixin, ModelSQL, ModelView):
     __name__ = 'ir.model.field.access'