posts: inline partials in posts/index template.

Make the posts/index template easier to read by putting everything in
one file, instead of splitting it up into a bunch of partials that
aren't used anywhere else.

app/helpers/posts_helper.rb

@@ -8,15 +8,11 @@ module PostsHelper
   end
 
   def missed_post_search_count_js(tags)
-    return unless reportbooru_enabled?
-
     sig = generate_reportbooru_signature(tags)
     render "posts/partials/index/missed_search_count", sig: sig
   end
 
   def post_search_count_js(tags)
-    return unless reportbooru_enabled?
-
     sig = generate_reportbooru_signature("ps-#{tags}")
     render "posts/partials/index/search_count", sig: sig
   end