Make the replication logger quieter (#4108)

changelog.d/4108.misc

@@ -0,0 +1 @@
+The "Received rdata" log messages on workers is now logged at DEBUG, not INFO.

synapse/replication/tcp/client.py

@@ -106,7 +106,7 @@ class ReplicationClientHandler(object):
 
         Can be overriden in subclasses to handle more.
         """
-        logger.info("Received rdata %s -> %s", stream_name, token)
+        logger.debug("Received rdata %s -> %s", stream_name, token)
         return self.store.process_replication_rows(stream_name, token, rows)
 
     def on_position(self, stream_name, token):