minor #5638 Update page_creation.rst (jeromenadaud)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5638).

Discussion
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Update page_creation.rst

Commits
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1df9453 Update page_creation.rst

book/page_creation.rst

@@ -43,7 +43,7 @@ a method inside of it that will be executed when someone goes to ``/lucky/number
     use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
     use Symfony\Component\HttpFoundation\Response;
 
-    class LuckyController
+    class LuckyController extends Controller
     {
         /**
          * @Route("/lucky/number")