Use new security.authorization_checker service

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.6+
| Fixed tickets |

Replace deprecated `security.context` with the `security.authorization_checker` service.
this place should use the new ``$this->isGranted()`` IMO, because it says to use the shortcut just above (and it could even use the ``denyAccessUnlessGranted`` shortcut)