Remove DockerHub images of pebble and pebble-challtestsrv

[sheurich]

Having old images on hub.docker.com could be confusing.
These should be removed:

• https://hub.docker.com/r/letsencrypt/pebble
• https://hub.docker.com/r/letsencrypt/pebble-challtestsrv

[mcpherrinm]

We will likely want to keep them up for a little bit, as I do know some people are pulling from there.

But I agree we'll likely want to remove them soon.

[mcpherrinm]

I've edited the dockerhub description to point to the Github Container Registry so at least anyone who looks there can find a way forward.

[consideRatio]

I was using it in https://github.com/jupyterhub/pebble-helm-chart, but saw now that new releases has been made but no new releases had been made in dockerhub.

I'll switch over to ghcr.io/letsencrypt/pebble.

---

• Leaving them around is sensible to allow people time to migrate without breaking
• Removing them is a way to force a migration, which can help ensure users aren't missing out on new versions.

I figure if new versions are security critical, removing them becomes relevant to do faster as compared to if its not.

I suggest setting a date for removal and going with it, clearly announcing the action point of migrating to ghcr.io/ before that date.

[mcpherrinm]

Because pebble is often or even usually used in CI, we probably want to prioritize not breaking people. It seems unlikely to me there is any security issue that will be significant against Pebble. We are not in any rush to deprecate the older Docker Hub images.