[FrameworkBundle] Fix visibility of a test helper

Author: dunglas

src/Symfony/Bundle/FrameworkBundle/Tests/Controller/RedirectControllerTest.php

@@ -290,7 +290,7 @@ private function createRedirectController($httpPort = null, $httpsPort = null)
         return $controller;
     }
 
-    public function assertRedirectUrl(Response $returnResponse, $expectedUrl)
+    private function assertRedirectUrl(Response $returnResponse, $expectedUrl)
     {
         $this->assertTrue($returnResponse->isRedirect($expectedUrl), "Expected: $expectedUrl\nGot:      ".$returnResponse->headers->get('Location'));
     }