Disable cleanup

The poster below completely misses the point. The issue is we want to disable any automatic cleanup completely. Turning the option into an error is obtuse.

This was fixed in v2.1.89 — cleanupPeriodDays: 0 is now rejected as invalid (with an error shown in /status) instead of silently disabling all transcript persistence. If you're still seeing this in the latest version, please comment with your version and repro and we'll reopen.

_Originally posted by @ashwin-ant in #23710_