Fix that the focus-out notification got sent deferred

Currently the window receives a focus-out notification, directly after
it popup, because currently the signal is sent deferred.
The original intention was that the previously focused window must
receive a focus-out notification.
This change makes the notification more precise by only sending the
focus-out to the previously focused window.

scene/main/window.cpp

@@ -1624,7 +1624,15 @@ void Window::popup(const Rect2i &p_screen_rect) {
 		// Send a focus-out notification when opening a Window Manager Popup.
 		SceneTree *scene_tree = get_tree();
 		if (scene_tree) {
-			scene_tree->notify_group_flags(SceneTree::GROUP_CALL_DEFERRED, "_viewports", NOTIFICATION_WM_WINDOW_FOCUS_OUT);
+			List<Node *> list;
+			scene_tree->get_nodes_in_group("_viewports", &list);
+			for (Node *n : list) {
+				Window *w = Object::cast_to<Window>(n);
+				if (w && !w->get_embedder() && w->has_focus()) {
+					w->_event_callback(DisplayServer::WINDOW_EVENT_FOCUS_OUT);
+					break;
+				}
+			}
 		}
 	}