Use KDE_INSTALL_LOGGINGCATEGORIESDIR in ECM 5.59

Summary: KDE_INSTALL_LOGGINGCATEGORIESDIR is provided for this use case now.

Test Plan: Installed, worked.

Reviewers: vkrause

Reviewed By: vkrause

Subscribers: vkrause

Differential Revision: https://phabricator.kde.org/D22650