Revert "potential fix for some AU plugin UIs not displaying"

This reverts commit e8fe35d96e.

gtk2_ardour/au_pluginui.mm

@@ -813,11 +813,12 @@ AUPluginUI::lower_box_size_allocate (Gtk::Allocation& allocation)
 gboolean
 AUPluginUI::lower_box_expose (GdkEventExpose* event)
 {
+#if 0 // AU view magically redraws by itself
 	[au_view drawRect:NSMakeRect(event->area.x,
 			event->area.y,
 			event->area.width,
 			event->area.height)];
-
+#endif
 	/* hack to keep ardour responsive
 	 * some UIs (e.g Addictive Drums) completely hog the CPU
 	 */