vo: fix non-sense in init code

I assume this was intended to generate an initial change event in order
to make the user read the initial values.

video/out/vo.c

@@ -755,7 +755,7 @@ static void *vo_thread(void *ptr)
         return NULL;
 
     update_display_fps(vo);
-    vo_event(vo, VO_WIN_STATE_MINIMIZED);
+    vo_event(vo, VO_EVENT_WIN_STATE);
 
     while (1) {
         mp_dispatch_queue_process(vo->in->dispatch, 0);