Maintenance: StatsStore column related_o_id is never used.

db/migrate/20120101000001_create_base.rb

@@ -685,7 +685,6 @@ class CreateBase < ActiveRecord::Migration[4.2]
       t.references :stats_store_object,             null: false
       t.integer :o_id,                              null: false
       t.string  :key,                   limit: 250, null: true
-      t.integer :related_o_id,                      null: true
       t.integer :related_stats_store_object_id,     null: true
       t.string  :data,                 limit: 5000, null: true
       t.integer :created_by_id,                     null: false