[book] fixes typo about redirect status codes in the controller chapter.

book/controller.rst

@@ -438,7 +438,7 @@ If you want to redirect the user to another page, use the ``redirectToRoute()``
         return $this->redirectToRoute('homepage');
 
         // redirectToRoute is equivalent to using redirect() and generateUrl() together:
-        // return $this->redirect($this->generateUrl('homepage'), 301);
+        // return $this->redirect($this->generateUrl('homepage'));
     }
 
 .. versionadded:: 2.6