DEV: Enable unless cops

We discussed the use of `unless` internally and decided to enforce
available rules from rubocop to restrict its most problematic uses.

lib/post_jobs_enqueuer.rb

@@ -44,7 +44,7 @@ class PostJobsEnqueuer
   def make_visible
     return if @topic.private_message?
     return unless SiteSetting.embed_unlisted?
-    return unless @post.post_number > 1
+    return if @post.post_number == 1
     return if @topic.visible?
     return if @post.post_type != Post.types[:regular]