Also purge redactions when purging events

Previously redacints where left behind leading to backfilling issues
when the server stumbled across the already existing yet to be
backfilled redactions.

This issues has been discussed in #8707.

Signed-off-by: Andreas Rammhold <[email protected]>

Author: andir

changelog.d/10343.bugfix

@@ -1 +1 @@
-Fix duplicate key error during backfilling of redaction events that were not deleted by the history purge job. Contributed by Andreas Rammhold (@andir).
+Fix errors during backfill caused by previously purged redaction events. Contributed by Andreas Rammhold (@andir).

synapse/storage/databases/main/purge_events.py

@@ -215,6 +215,7 @@ def _purge_history_txn(
             "event_relations",
             "event_search",
             "rejections",
+            "redactions",
         ):
             logger.info("[purge] removing events from %s", table)