fix maximize callback not getting deregisterd

dwl.c

@@ -1276,6 +1276,7 @@ destroynotify(struct wl_listener *listener, void *data)
 		wl_list_remove(&c->commit.link);
 		wl_list_remove(&c->map.link);
 		wl_list_remove(&c->unmap.link);
+		wl_list_remove(&c->maximize.link);
 	}
 	free(c);
 }