fix: make ScheduledNotifications a TimedJob and run every minute

[salmart-dev]

Summary

This PR is a follow-up to address issues discovered while investigating issue https://github.com/nextcloud/server/issues/49584

When running occ background-job:worker, some jobs can be seen running constantly and ScheduledNotifications is one of them. It should be safe to run the rotation job every second.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• [ ] Tests (unit, integration, api and/or acceptance) are included
• [ ] Screenshots before/after for front-end changes
• [ ] Documentation (manuals or wiki) has been updated or is not required
• [ ] Backports requested where applicable (ex: critical bugfixes)