Update generator templates

generator_templates/active_record/migration/create_table_migration.rb

@@ -3,7 +3,7 @@
 # See http://doc.gitlab.com/ce/development/migration_style_guide.html
 # for more information on how to write migrations for GitLab.
 
-class <%= migration_class_name %> < ActiveRecord::Migration
+class <%= migration_class_name %> < ActiveRecord::Migration[<%= ActiveRecord::Migration.current_version %>]
   include Gitlab::Database::MigrationHelpers
 
   # Set this constant to true if this migration requires downtime.

generator_templates/active_record/migration/migration.rb

@@ -3,7 +3,7 @@
 # See http://doc.gitlab.com/ce/development/migration_style_guide.html
 # for more information on how to write migrations for GitLab.
 
-class <%= migration_class_name %> < ActiveRecord::Migration
+class <%= migration_class_name %> < ActiveRecord::Migration[<%= ActiveRecord::Migration.current_version %>]
   include Gitlab::Database::MigrationHelpers
 
   # Set this constant to true if this migration requires downtime.

generator_templates/rails/post_deployment_migration/migration.rb

@@ -3,7 +3,7 @@
 # See http://doc.gitlab.com/ce/development/migration_style_guide.html
 # for more information on how to write migrations for GitLab.
 
-class <%= migration_class_name %> < ActiveRecord::Migration
+class <%= migration_class_name %> < ActiveRecord::Migration[<%= ActiveRecord::Migration.current_version %>]
   include Gitlab::Database::MigrationHelpers
 
   DOWNTIME = false