Rollup merge of #144757 - Muscraft:triagebot-emitter-pings, r=lqd

Ping Muscraft when emitter change

While I am working towards `annotate-snippets` being the default emitter for `rustc`, it would be helpful if I were pinged when the default emitter is modified so that I can more easily maintain parity in output between `rustc` and `annotate-snippets`.

Author: jhpratt