Remove knock-related schema update

Because DINUM had it before mainline, so the file names don't match.
Will need some fiddling with the database before updating to a mainlined
version.

synapse/storage/schema/main/delta/59/11add_knock_members_to_stats.sql

@@ -1,20 +0,0 @@
-/* Copyright 2020 Sorunome
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *    http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
--- Existing rows will default to NULL, so anything reading from these tables
--- needs to interpret NULL as 0. This is fine here as no existing rooms can have
--- any knocked members.
-ALTER TABLE room_stats_current ADD COLUMN knocked_members INT;
-ALTER TABLE room_stats_historical ADD COLUMN knocked_members BIGINT;