Fixed commented namespace for file location on bundle config.

Author: richsage

cookbook/bundles/extension.rst

@@ -435,7 +435,7 @@ can help with merging, validation, default values, and format normalization.
 To take advantage of this system, you'll create a ``Configuration`` class
 and build a tree that defines your configuration in that class::
 
-    // src/Acme/HelloBundle/DependencyExtension/Configuration.php
+    // src/Acme/HelloBundle/DependencyInjection/Configuration.php
     namespace Acme\HelloBundle\DependencyInjection;
 
     use Symfony\Component\Config\Definition\Builder\TreeBuilder;