pointer: Remove focus listener

It's added too late to matter -- by the time we've destroyed the
resource, we've already repicked and re-set the focus.

src/wayland/meta-wayland-pointer.h

@@ -48,7 +48,6 @@ struct _MetaWaylandPointer
   struct wl_list resource_list;
   MetaWaylandSurface *focus;
   struct wl_resource *focus_resource;
-  struct wl_listener focus_listener;
   guint32 focus_serial;
   guint32 click_serial;