Don't show the OrientationSensor if it's not supported

Test Plan: I don't get the OrientationSensor SNI on my laptop, which is fine, because it was useless.

Reviewers: #kwin, #plasma, zzag

Reviewed By: #kwin, #plasma, zzag

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D19955