Use a new Ruby 3.0 pipeline schedule

What does this MR do and why?

• Rename 2-hourly scheduled pipelines to maintenance scheduled pipelines
• Add a new Ruby 3.0 maintenance pipeline schedule. Set it to run every 2 hours at odd hour so they don't run at the same time, but with the same frequency

TODO before merge

• Add SCHEDULE_TYPE to the maintenance schedules (previously 2-hourly). Set it to maintenance
  • (Has to be logged in as @gitlab-bot to check) https://gitlab.com/gitlab-org/gitlab/-/pipeline_schedules/23503/edit
  • Interval cron: 5 */2 * * *
  • Extra variable: OMNIBUS_GITLAB_CACHE_UPDATE set to true
• Add another pipeline schedule which sets SCHEDULE_TYPE to maintenance. Also set RUBY_VERSION to 3.0. Set it to run the other 2-hourly from the current one
  • (Has to be logged in as @gitlab-bot to check) https://gitlab.com/gitlab-org/gitlab/-/pipeline_schedules/257835/edit
  • Interval cron: 5 1-23/2 * * *

TODO after merged

• Remove FREQUENCY in the pipeline schedules
• Activate the new schedule: [2-hourly] [maintenance] [Ruby3] Repo caching, Review Apps cleanup, Caches update (Has to be logged in as @gitlab-bot to check) https://gitlab.com/gitlab-org/gitlab/-/pipeline_schedules/257835/edit

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Related to #340298 (closed)