Fix node config warning not updating for Multiplayer{Spawner,Synchronizer}

(cherry picked from commit 6feb43200b95168dda261573ca1765a67b8a0fff)

modules/multiplayer/multiplayer_spawner.cpp

@@ -251,6 +251,7 @@ NodePath MultiplayerSpawner::get_spawn_path() const {
 void MultiplayerSpawner::set_spawn_path(const NodePath &p_path) {
 	spawn_path = p_path;
 	_update_spawn_node();
+	update_configuration_warnings();
 }
 
 void MultiplayerSpawner::_track(Node *p_node, const Variant &p_argument, int p_scene_id) {

modules/multiplayer/multiplayer_synchronizer.cpp

@@ -354,6 +354,7 @@ void MultiplayerSynchronizer::set_root_path(const NodePath &p_path) {
 	_stop();
 	root_path = p_path;
 	_start();
+	update_configuration_warnings();
 }
 
 NodePath MultiplayerSynchronizer::get_root_path() const {