fennec nightly builds are missing since may 17th, 2019

[willkg]

Looks like buildhub isn't getting fennec nightly build data since may 17th, 2019.

https://mozilla-services.github.io/buildhub/?channel[0]=nightly&products[0]=fennec

[willkg]

I deprecated this project, so I'd rather not spend time looking into this.

If it turns out we don't get everyone over to buildhub2 in the next couple of weeks or some other compelling reason comes up to deal with this now, I'll look into this.