List removed community/group worker endpoints in upgrade.md

[olmari]

I'd expect to see community worker endpoints that are going to be nuked in Synapse 1.61 ( https://github.com/matrix-org/synapse/pull/12936/files#diff-4eef4606c1f655c8f2b04944a322717d2dfe2a32f6df6df8403dad7ebdd00052 ) to be listed in Synapse upgrade notes at release time.

Reasoning: It is easy to check current state of existing endpoints from workers.md, but opposite is not true, surprisingly hard to determine does one have an endpoint in their config that is not listed on workers.md anymore. So at least upgrade notes should reveal "these endpoints are removed, go check your worker config".

[olmari]

Alternate/adjacent idea was to have some kind of "historical endpoints" section on workers.md. While nice idea in itself especially for not so pedantically up to date keeping server admin, I feel upgrade notes is exactly proper place to tell which (worker) endpoints going EOL.

[clokep]

Would you be willing to make a PR including this information?

[olmari]

Well I can easily copypaste the endpoints, I can do that and Wrote description and base for next upgrade.md, I'll leave making doc looking proper to devs :)

[clokep]

Related to #11584.