perf runner machine description outdated after switching to new one

[klensy]

This https://github.com/rust-lang/rustc-perf/blob/master/docs/perf-runner.md not currently true? Part of new config i found at https://github.com/rust-lang/simpleinfra/blob/master/ansible/playbooks/rustc-perf.yml.

[Kobzol]

Good point, thanks! #2182 fixes this.