Mark as deprecated and set an expiry date. Upstream has announced end
of life as 1st February 2021, so there should be plenty of time for
people to migrate to the current version: RT-5.0

https://bestpractical.com/blog/2020/7/announcing-end-of-life-for-request-tracker-42-and-request-tracker-for-incident-response-32-series
https://bestpractical.com/release-policy