minor symfony#3856 Update voters_data_permission.rst (MarcomTeam)

This PR was submitted for the 2.4 branch but it was merged into the 2.3 branch instead (closes symfony#3856).

Discussion
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Update voters_data_permission.rst

Strange $product variable...

Commits
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a392e78 Update voters_data_permission.rst
a2d022b Update voters_data_permission.rst

Author: weaverryan

cookbook/security/voters_data_permission.rst

@@ -204,20 +204,16 @@ from the security context is called.
 
     class PostController extends Controller
     {
-        public function showAction()
+        public function showAction($id)
         {
             // get a Post instance
             $post = ...;
-
+            
             // keep in mind, this will call all registered security voters
             if (false === $this->get('security.context')->isGranted('view', $post)) {
                 throw new AccessDeniedException('Unauthorised access!');
             }
 
-            $product = $this->getDoctrine()
-                ->getRepository('AcmeStoreBundle:Post')
-                ->find($id);
-
             return new Response('<h1>'.$post->getName().'</h1>');
         }
     }