wayland: Only repick pointer on crossing events

These are the only situations where it makes sense to determine a new
focus surface.

Suggested-by: Jonas Dreßler <verdre@v0yd.nl>
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1654>

src/wayland/meta-wayland-pointer.c

@@ -611,6 +611,8 @@ void
 meta_wayland_pointer_update (MetaWaylandPointer *pointer,
                              const ClutterEvent *event)
 {
+  if (event->type == CLUTTER_ENTER ||
+      event->type == CLUTTER_LEAVE)
     repick_for_event (pointer, event);
 
   if (event->type == CLUTTER_MOTION ||