HOLD: Hide erroneous featured comments

Small tweak to hide unfeatured comments from featured box when they've been returned by a cached VIP query.

https://github.com/GigaOM/gigaom/issues/5097
https://github.com/GigaOM/gigaom/issues/5104

Related:
https://github.com/GigaOM/gigaom-plugins/pull/2536
Are you sure the caching isn't happening in https://github.com/methnen/bsocial-comments/blob/hide-featured/components/class-bsocial-comments-featured.php#L508 ?

I don't see anything that invalidates the cache when the featured posts are changed.