Removed date filter from failed_list.html.twig

Otherwise you get this error:

An exception has been thrown during the rendering of a template ("DateTime::__construct(): Failed to parse time string (di mrt 26 12:46:53 UTC 2013) at position 0 (d): The timezone could not be found in the database") in BCCResqueBundle:Default:failed_list.html.twig at line 21.

This is because PHP-Resque uses a localized timestamp: 
````php
$data->failed_at = strftime('%a %b %d %H:%M:%S %Z %Y');
````