[wwwdocs] Generalize instructions and remove notes on repository mirroring via rsync.

[Gerald Pfeifer]

[ gcc-patches -> gcc ]

On Sat, 18 Jan 2020, Gerald Pfeifer wrote:
> Remove all references how to perform local checkouts, to SVN, and
> mirroring the repository.  Instead generalize descriptions since
> with the move to Git syncing the repository with rsync and then
> checking out locally became mostly pointless.

The rsync overview shows

  gcc-svn         gcc svn repository ()
  gcc-cvs         gcc cvs repository ()

I assume it's intentional that git is not listed there?

Should gcc-cvs really be listed there still?  (If no, should we
at this point prune the old CVS tree on the server?)

Gerald