api: remove available_includes dependent on current user.

This is to avoid specifying permissions in multiple disjoint places and
because most API users shouldn't need these fields.

app/models/comment.rb

@@ -166,8 +166,6 @@ class Comment < ApplicationRecord
   end
 
   def self.available_includes
-    includes_array = [:post, :creator, :updater]
-    includes_array << :moderation_reports if CurrentUser.is_moderator?
-    includes_array
+    [:post, :creator, :updater]
   end
 end