Summary: This patch lets the Colors, Notifications, and Accessibility KCMs display proper tooltip that contains their captions, rather than useless tooltips that reveals the now-obsolete implementation detail that the KCMs are the only items in their single-item categories.

Test Plan:
For example the Colors KCM, before: {F6558586}

After: {F6558588}

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: rapiteanu, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D18413