st/drawing-actor: Queue redraw when repainting
Commit e7734e30 removed the clutter_content_invalidate() call that took care of queuing a redraw for us. Now that we no longer delegate to a content we have to do that ourselves.
Fixes: e7734e30 ("st/drawing-area: Merge ClutterCanvas to StDrawingArea") Closes: #7397 (closed)