[Cryptech Core] upgrade warning for bikeshed.cryptech.is

[Rob Austein]

Mandatory OS upgrade pending for the server in Reykjavik which handles
Cryptech email, git, and wiki.  It's a minor version bump, I've
already installed it on one of my own servers with no ill effects, and
yes of course we have backups, but services will be down for a little
while for safety during the installation phase.

Download and staging of upgrade will commence immediately, but those
phases take long enough that this message should have plenty of time
to go out before I shut down services.

I'll send another message when we're up with the new release.  I'll be
on Slack if something goes horribly wrong with the upgrade.