Fix phpunit test failure.

Closes #3434218

src/DeviceHtmlRouteProvider.php

@@ -30,7 +30,13 @@ class DeviceHtmlRouteProvider extends AdminHtmlRouteProvider {
   }
 
   /**
-   * {@inheritdoc}
+   * ResponsivePreview constructor.
+   *
+   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
+   *   The entity type.
+   *
+   * @return Symfony\Component\Routing\Route|null
+   *   returns route.
    */
   protected function getCollectionRoute(EntityTypeInterface $entity_type): ?Route {
     if ($entity_type->hasLinkTemplate('collection') && $entity_type->hasListBuilderClass()) {