Eugeni greylisting own our services

While working on email deliverability tests in the context of #41063 (closed), I noticed that eugeni was greylisting mail sent from servers in our own infrastructure.

And indeed, looking at the postgrey configuration in /etc/postgrey, we see it's exempting debian.org machines, but not our own...

So I think we should add a torproject.org entry in /etc/postgrey/whitelist_clients on eugeni, and manage those configs through Puppet.

This will ensure that services relaying mail though eugeni (Discourse, GitLab, RT, CiviCRM...) aren't needlessly delayed.