Made sqlite's remove_field behave like the base backend.

            # For explicit "through" M2M fields, do nothing

        # For everything else, remake.

        else:

            # It might not actually have a column behind it

            if field.db_parameters(connection=self.connection)['type'] is None:

                return

            self._remake_table(model, delete_fields=[field])

    def _alter_field(self, model, old_field, new_field, old_type, new_type, old_db_params, new_db_params, strict=False):