Drop kdeinit linking

Summary:
This wasn't used on startup (ksmserver calls KProcess)
Nor for the rules dialog (kwin invokes it with QProcess)

We may as well simplify the code and drop the dependency

See also T12140

Test Plan:
Restarted
Opened the rules dialog

Reviewers: #kwin, zzag

Reviewed By: #kwin, zzag

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D26835