Use default_value_for to set notified_of_own_activity instead of using a DB migration

app/models/user.rb

@@ -22,6 +22,7 @@ class User < ActiveRecord::Base
   default_value_for :hide_no_ssh_key, false
   default_value_for :hide_no_password, false
   default_value_for :project_view, :files
+  default_value_for :notified_of_own_activity, false
 
   attr_encrypted :otp_secret,
     key:       Gitlab::Application.secrets.otp_key_base,

db/post_migrate/20170317131326_add_notified_of_own_activity_default.rb

@@ -1,20 +0,0 @@
-class AddNotifiedOfOwnActivityDefault < ActiveRecord::Migration
-  include Gitlab::Database::MigrationHelpers
-  disable_ddl_transaction!
-
-  DOWNTIME = false
-
-  def up
-    begin
-      update_column_in_batches(:users, :notified_of_own_activity, false) do |table, query|
-        query.where(table[:notified_of_own_activity].eq(nil))
-      end
-
-      change_column :users, :notified_of_own_activity, :boolean, default: false, null: false
-    end
-  end
-
-  def down
-    change_column_default :users, :notified_of_own_activity, nil
-  end
-end

db/schema.rb

@@ -1236,7 +1236,7 @@ ActiveRecord::Schema.define(version: 20170317203554) do
     t.string "organization"
     t.boolean "authorized_projects_populated"
     t.boolean "ghost"
-    t.boolean "notified_of_own_activity", default: false, null: false
+    t.boolean "notified_of_own_activity"
   end
 
   add_index "users", ["admin"], name: "index_users_on_admin", using: :btree