Removes unnecessary override of field_from_activity on foreign key

bookwyrm/models/fields.py

@@ -126,14 +126,6 @@ class ForeignKey(ActivitypubRelatedFieldMixin, models.ForeignKey):
             return None
         return value.remote_id
 
-    def field_from_activity(self, value):
-        try:
-            validate_remote_id(value)
-        except ValidationError:
-            return None
-        return activitypub.resolve_remote_id(self.related_model, value)
-
-
 
 class OneToOneField(ActivitypubRelatedFieldMixin, models.OneToOneField):
     ''' activitypub-aware foreign key field '''