Merge branch '299078-add-comment-for-rails-upgrade' into 'master'

Add exception when Rails is upgraded

See merge request gitlab-org/gitlab!63431

lib/gitlab/database/postgresql_adapter/empty_query_ping.rb

 # frozen_string_literal: true
 
+# This patch will be included in the next Rails release: https://github.com/rails/rails/pull/42368
+raise 'This patch can be removed' if Rails::VERSION::MAJOR > 6
+
 # rubocop:disable Gitlab/ModuleWithInstanceVariables
 module Gitlab
   module Database