[containments/desktop] Use new colorful filter icon
Summary:
Test Plan: Open the desktop configuration dialog.
Reviewers: Plasma, VDG, ngraham
Reviewed By: VDG, ngraham
Subscribers: plasma-devel, VDG, Plasma
Tags: Plasma
Maniphest Tasks: T10165
Differential Revision: https://phabricator.kde.org/D24228