fix active record induced error on postgres by removing distinct.

Inlining the code did not turn out well, as we have to cope with the polymorphic association of user here..

app/models/request_for_comment.rb

@@ -47,10 +47,10 @@ class RequestForComment < ApplicationRecord
 
   def commenters
     commenters = []
-    comments.distinct.to_a.each {|comment|
+    comments.each {|comment|
       commenters.append comment.user
     }
-    commenters.uniq {|user| user.id}
+    commenters.uniq
   end
 
   def self.with_last_activity