[kcmkwin/kwineffects] Use new Kirigami ListSectionHeader component

Summary:

Test Plan: Open the Desktop Effects KCM.

Reviewers: KWin, Plasma, VDG, davidedmundson, ngraham

Reviewed By: KWin, Plasma, VDG, davidedmundson, ngraham

Subscribers: ngraham, kwin, VDG, Plasma, KWin

Tags: KWin

Differential Revision: https://phabricator.kde.org/D23913