[#10308] add use statement and fix array

Author: xabbuh

doctrine/event_listeners_subscribers.rst

@@ -172,15 +172,16 @@ interface and have an event method for each event it subscribes to::
     use Doctrine\Common\EventSubscriber;
     // for Doctrine < 2.4: use Doctrine\ORM\Event\LifecycleEventArgs;
     use Doctrine\Common\Persistence\Event\LifecycleEventArgs;
+    use Doctrine\ORM\Events;
     use AppBundle\Entity\Product;
 
     class SearchIndexerSubscriber implements EventSubscriber
     {
         public function getSubscribedEvents()
         {
             return array(
-                \Doctrine\ORM\Events::postPersist => 'postPersist',
-                \Doctrine\ORM\Events::postUpdate => 'postUpdate',
+                Events::postPersist,
+                Events::postUpdate,
             );
         }