Add a new ruby3 maintenance pipeline schedule

Add a new ruby3 maintenance pipeline schedule.

Currently we're relying on push pipelines to run ruby3 pipelines, and there's no scheduled maintenance one to update cache and run more jobs. It was done so due to #367867 (closed)

Now that ruby3 is on its own branch, the review app should not be stepping on the default branch one. We should be able to add this again.

Advantages:

• We can have up-to-date cache for ruby3
• We'll run more jobs in case push pipeline can't cover everything

Things to consider:

• We still run push pipelines every 2 hours, so it can be stepping on it, cancelling each others. Need to make sure this didn't happen often, or don't make it happen at all

Also see: #378981 (comment 1165642857)