Prevent upsert operation

Only works in newer postgresql, but also not really necessary because
the table is brandnew there.

db/migrate/20180812173710_copy_status_stats.rb

@@ -9,8 +9,6 @@ class CopyStatusStats < ActiveRecord::Migration[5.2]
           SELECT id, reblogs_count, favourites_count, created_at, updated_at
           FROM statuses
           WHERE id IN (#{statuses.map(&:id).join(', ')})
-          ON CONFLICT (status_id) DO UPDATE
-          SET reblogs_count = EXCLUDED.reblogs_count, favourites_count = EXCLUDED.favourites_count
         SQL
       end
     end