Update download URLs

Commit ee733f9d (version up: zc.buildout 2.7.1+slapos017,
slapos.libnetworkcache 0.23, 2022-03-28) introduced a new way of
computing cache key used for shacache and downlaod URLs that were only
in cache but no longer available from their original location no longer
could be retrieved. This update the original download URLs to URLs that
are valid today.

See merge request nexedi/slapos!1147