Backups are moving from GleSYS to Yandex Cloud (is this motivated by me not
having to pay for them in that case? Maybe!); this changes the default backup
location to accommodate that.
I also noticed that we previously manually placed the backup key on whitby, so
the new key is going into agenix instead, as well as the secrets for protecting
the repositories.
Change-Id: Ibe5dbfec6784345f020a8b4d92bb01c6ad719a89
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13096
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
84bdb1e89a