[effects/morphingpopups] Use enumerators from the DataRole enum
Summary:
Use Effect.WindowForceBackgroundContrastRole and Effect.WindowForceBlurRole
instead of integers to improve readability.
Reviewers: KWin, broulik
Reviewed By: broulik
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D15709