Use the is_granted expression to keep consistency with php example above

As `has_role` only check for roles without calling the voter, it does not do the same job that
`$this->get('security.context')->isGranted('ROLE_ADMIN')`

So it is quiete confusing.

Author: tyx

book/security.rst

@@ -1091,7 +1091,7 @@ Thanks to the SensioFrameworkExtraBundle, you can also secure your controller us
     use Sensio\Bundle\FrameworkExtraBundle\Configuration\Security;
 
     /**
-     * @Security("has_role('ROLE_ADMIN')")
+     * @Security("is_granted('ROLE_ADMIN')")
      */
     public function helloAction($name)
     {