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