debian-doc files on the Debian web server

Hi,

I finally made update to the cron script so we don't rely on FTP protocol.
url = [email protected]:webmaster-team/cron.git  

  526ebd0 ("Download deb via HTTP", 2021-11-01)

    No more use of FTP protocol
    
    Ensure to avoid unnecessary downloads of non-sid packages and already
    downloaded packages.
    
    unpack once and do not reprocess
    
    Signed-off-by: Osamu Aoki <[email protected]>
    

I stop making a copy of doc.  I don't see the following data are used any more.
> $crondir/ftpfiles/doc

Although it was tested on my machine, since this is rather big change, I am afraid
something may break.

Holger: You are building installation-guide from source.  Even though this is on
'lessoften' side, it is quite heavy process.  Since new 7doc can handle stable and
oldstable, using 7doc may be an idea.

Regards,

Osamu