[SecurityBundle] add note to info text of no-op config option logout_on_user_change

Author: dmaicher

src/Symfony/Bundle/SecurityBundle/DependencyInjection/MainConfiguration.php

@@ -199,7 +199,7 @@ private function addFirewallsSection(ArrayNodeDefinition $rootNode, array $facto
             ->scalarNode('context')->cannotBeEmpty()->end()
             ->booleanNode('logout_on_user_change')
                 ->defaultTrue()
-                ->info('When true, it will trigger a logout for the user if something has changed.')
+                ->info('When true, it will trigger a logout for the user if something has changed. Note: No-Op option since 4.0. Will always be true.')
             ->end()
             ->arrayNode('logout')
                 ->treatTrueLike(array())