Remove check_plain from forum topic list title

Omega does double check_plain() to the $topic->title at forum-topic-list.tpl.php, while template_preprocess_forum_topic_list() #1168 has already done it for either the shadow copy check_plain() or topic title link via l() function.
This results in un-expected plain HTML markups rather than actual link for the latter.

The doc at the top of the file confirms:

$topic->title: The title of the topic. Safe to output.

Regards,
gaus