[FrmaeworkBundle] More simplifications in the DI configuration

src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Configuration.php

@@ -339,10 +339,7 @@ class Configuration implements ConfigurationInterface
                                         ->defaultNull()
                                     ->end()
                                     ->arrayNode('initial_marking')
-                                        ->beforeNormalization()
-                                            ->ifTrue(function ($v) { return !\is_array($v); })
-                                            ->then(function ($v) { return [$v]; })
-                                        ->end()
+                                        ->beforeNormalization()->castToArray()->end()
                                         ->defaultValue([])
                                         ->prototype('scalar')->end()
                                     ->end()