Fix query performance for /sync (#12745)

changelog.d/12745.bugfix

+Fix DB performance regression introduced in v1.59.0rc2.

synapse/storage/databases/main/stream.py

@@ -750,7 +750,7 @@ class StreamWorkerStore(EventsWorkerStore, SQLBaseStore):
                 WHERE room_id = ?
                     AND stream_ordering <= ?
                     AND NOT outlier
-                    AND rejections.reason IS NULL
+                    AND rejections.event_id IS NULL
                 ORDER BY stream_ordering DESC
                 LIMIT 1
             """