Hide update notifier completely when no updates are available
Summary: The applet isn't particularly useful when no updates are available. Hide it to reduce the clutter
Reviewers: ngraham, apol, Discover Software Store
Reviewed By: ngraham
Subscribers: plasma-devel
Tags: Plasma
Maniphest Tasks: T11125
Differential Revision: https://phabricator.kde.org/D21941