Merge branch 'deprecated-migration-inheritance' into 'master'

Directly inheriting from ActiveRecord::Migration is deprecated

See merge request gitlab-org/gitlab-ce!25066

changelogs/unreleased/deprecated-migration-inheritance.yml

+---
+title: Directly inheriting from ActiveRecord::Migration is deprecated
+merge_request: 25066
+author: Jasper Maes
+type: other

db/migrate/20181027114222_add_first_day_of_week_to_user_preferences.rb

 # frozen_string_literal: true
 
-class AddFirstDayOfWeekToUserPreferences < ActiveRecord::Migration
+class AddFirstDayOfWeekToUserPreferences < ActiveRecord::Migration[5.0]
   DOWNTIME = false
 
   def change

db/migrate/20181028120717_add_first_day_of_week_to_application_settings.rb

 # frozen_string_literal: true
 
-class AddFirstDayOfWeekToApplicationSettings < ActiveRecord::Migration
+class AddFirstDayOfWeekToApplicationSettings < ActiveRecord::Migration[5.0]
   include Gitlab::Database::MigrationHelpers
   disable_ddl_transaction!