[libkwineffects] Use Q_ENUM in AnimationEffect

Summary: Q_ENUMS is deprecated.

Test Plan: The Window Aperture effect still works.

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D17587