Use the text rather than highlight color for rating/star emblem
The problem with using the highlight color is that the emblem becomes invisible when
applied to a UI element that's selectable and (correctly) uses the default selection
color. Making it use the text color instead fixes the bug in all cases.
Stars in various UIs (Discover, Dolphin) are now black rather than blue, and the icon
can now be used on buttons without becoming invisible.
Reviewers: ndavis, VDG
Reviewed By: ndavis, VDG
Differential Revision: https://phabricator.kde.org/D24612