pq/listener: remove the regular info log of no notifications
pq/listener: remove the regular info log of no notifications

The log is initially intended for early debugging uses. It is
safe to remove the log now as the pq/listener run loop
has been proved to be quite stable.

SkygearIO/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server,rickmak/skygear-server,rickmak/skygear-server,SkygearIO/skygear-server,SkygearIO/skygear-server