Don't log "unknown member event" warnings

These just mean we haven't noticed any change in a profile event, and
haven't been of any use.

src/backend/nio_callbacks.py

@@ -556,7 +556,7 @@ class NioCallbacks:
                 "%1 changed their {}".format(" and ".join(changed)),
             )
 
-        log.warning("Unknown member event: %s", json.dumps(vars(ev), indent=4))
+        # log.warning("Unknown member ev.: %s", json.dumps(vars(ev), indent=4))
         return None