Resolve #3446311 "Drupal 11 compatibility"

Closes #3446311

src/EventSubscriber/FeedBlockCacheExpire.php

@@ -137,7 +137,7 @@ class FeedBlockCacheExpire implements EventSubscriberInterface {
    * @return array
    *   An array of event listener definitions.
    */
-  public static function getSubscribedEvents() {
+  public static function getSubscribedEvents(): array {
     $events[KernelEvents::RESPONSE][] = ['onRespond'];
     return $events;
   }