Fix errors from malformed log line (#7454)

changelog.d/7454.feature

+Add support for running replication over Redis when using workers.

synapse/replication/tcp/redis.py

@@ -96,7 +96,7 @@ class RedisSubscriber(txredisapi.SubscriberProtocol, AbstractConnection):
             cmd = parse_command_from_line(message)
         except Exception:
             logger.exception(
-                "[%s] failed to parse line: %r", message,
+                "Failed to parse replication line: %r", message,
             )
             return