Docker Hub contains old tsidp version

[dkaser]

tailscale/tsidp exists on Docker Hub, and is pushing updated tags, but is running an old version of the app. I'm not sure exactly which commit it's being built against, but it still has -allow-insecure-registration, so I'd guess that it might be the last version before the code was moved out of the main tailscale repo.

https://github.com/tailscale/tailscale/tree/main/cmd/tsidp still exists, maybe this needs to be cleaned up now?

This should either be fixed (to have the correct versions) or removed.

Discord conversation that prompted issue: https://discord.com/channels/1379528469859532931/1405948286090743829/1449759389010366485