Add forgotten use

Author: dvigo

security/access_denied_handler.rst

@@ -29,6 +29,7 @@ unauthenticated user tries to access a protected resource::
     use Symfony\Component\HttpFoundation\RedirectResponse;
     use Symfony\Component\HttpFoundation\Request;
     use Symfony\Component\HttpFoundation\Session\SessionInterface;
+    use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
     use Symfony\Component\Security\Core\Exception\AuthenticationException;
     use Symfony\Component\Security\Http\EntryPoint\AuthenticationEntryPointInterface;