Remove warning about old kiosk feature that no longer applies.

Summary:
The concept of KStandardDirs resources no longer exists;
and anyway kiosk users disable things at the feature level, not at
the config file level.

Test Plan: Compiles without warnings

Reviewers: davidedmundson, arichardson, broulik

Reviewed By: broulik

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D14829