resolved wrong namespace usage

Hi,

I had an error when posting a comment with only one character (FatalErrorException: Error: Class 'FOS\Rest\Util\Codes' not found in /Applications/MAMP/htdocs/Creapills/vendor/friendsofsymfony/comment-bundle/FOS/CommentBundle/Controller/ThreadController.php line 607), to fix this i updated the namespace of the Class Codes used in the Thread Controller.