minor symfony#5522 [create_framework] Add missing extract() 2nd arg (kenjis)

This PR was merged into the 2.3 branch.

Discussion
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[create_framework] Add missing extract() 2nd arg

See previous page: http://symfony.com/doc/2.3/create_framework/templating.html

The code is `extract($request->attributes->all(), EXTR_SKIP);`.

In this page, suddenly `EXTR_SKIP` is missing. I don't know why.

Commits
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0905395 Fix code

Author: wouterj

create_framework/http-kernel-controller-resolver.rst

@@ -160,7 +160,7 @@ Let's conclude with the new version of our framework::
 
     function render_template(Request $request)
     {
-        extract($request->attributes->all());
+        extract($request->attributes->all(), EXTR_SKIP);
         ob_start();
         include sprintf(__DIR__.'/../src/pages/%s.php', $_route);