fix redisplay of track headers after UI scale change

The suspend/resume routes code requires that there be a call to
Editor::redisplay_track_views() if anything is to happen on resume. This was
missing from the events triggered by a UI scale change.

gtk2_ardour/editor_canvas.cc

@@ -363,6 +363,7 @@ Editor::track_canvas_viewport_size_allocated ()
 	update_fixed_rulers();
 	update_tempo_based_rulers ();
 	redisplay_grid (false);
+	redisplay_track_views ();
 	_summary->set_overlays_dirty ();
 }