Drupal 11 fixes added.

Closes #3431546

src/EventSubscriber/LanguageHierarchyConfigEventSubscriber.php

@@ -26,7 +26,7 @@ class LanguageHierarchyConfigEventSubscriber implements EventSubscriberInterface
   /**
    * {@inheritdoc}
    */
-  public static function getSubscribedEvents() {
+  public static function getSubscribedEvents(): array {
     $events[ConfigEvents::IMPORT] = ['onConfigImport'];
     return $events;
   }