Site gen copies too much stuff

Take a look at https://gitlab.common-lisp.net/cmucl/cmucl-site/-/jobs/2395/artifacts/download and download the archive of artifacts. If you look at the contents, you'll find things like:

public/cmucl-www/FAQ.html, etc.
public/gen/*
public/texinfo/

So we basically have three copies of FAQ.html. The actual one we want, a copy in public/cmucl-www, and another in public/gen.

We also end up with two copies of the texinfo docs. We probably don't need public/texinfo.