Deprecate debomatic service

It was useful back when we were building our own Iceweasel, but thankfully we’re not doing that anymore… and hopefully we will manage to avoid building our own Icedove for too long (in practice, most people who may need to do that will want to do it locally these days anyway).

IIRC I was the only one using this service, and apparently, last time someone used it was in April, 2014. It wasn’t updated to match the fact that Jessie was released, and that Tails is based on Jessie.

So I think we should drop it now, and reclaim 2 vcpus, 2G of RAM, and 24G of disk space.

Of course we can revert the commits later and reinstall a VM if we ever need to bring it back.

Related issues

• Related to #11186 (closed)

Original created by @intrigeri on 11184 (Redmine)