Download directory no longer accessible, breaking cmucl CI

For a long time, we had release and snapshot tarballs at https://common-lisp.net/project/cmucl/downloads/. But this now no longer works and a 403 Forbidden error is returned. This also breaks cmucl's CI that pulls snapshot tarballs for running CI. According to https://gitlab.common-lisp.net/cmucl/cmucl/-/pipelines, it was working a week ago, but has now stopped working. I have no problem updating docs and CI to use a new path, but I don't know what it would be. (It still seems reachable via rsync, though.) -- Ray