remove reply from message journaling (#9293)

The columns:
* last_reply_id
* replies_count

are columns that exist for performance reasons only. They do not contain information about the message itself.

If they are journaled, adding a message to a forum updates the last_reply_id of the parent message. The user replying will then be shown to have updated the replied to message

db/migrate/20210519141244_remove_reply_from_message_journalizing.rb

@@ -0,0 +1,6 @@
+class RemoveReplyFromMessageJournalizing < ActiveRecord::Migration[6.1]
+  def change
+    remove_column :message_journals, :last_reply_id, :integer
+    remove_column :message_journals, :replies_count, :integer, default: 0, null: false
+  end
+end