[Style KCM] Make sure to enable kappmenu kded module

The old KCM enabled and disabled the kded (both autoloading and load/unloadModule) depending
on global menu setting.

Since we never had global menu in 5.x before, it would disable the menu when you hit Apply.
This will break global menu for users without an obvious reason why.

Differential Revision: https://phabricator.kde.org/D4199