Use contextually-appropriate icon for GlobalDrawer handle button
Summary:
Now that the GlobalDrawer's icon can be customized (see D23154), let's use a more
contextually-appropriate icon for Kamoso's GlobalDrawer, which has the effects in it
Test Plan:
Reviewers: VDG, apol
Reviewed By: apol
Differential Revision: https://phabricator.kde.org/D23160