As of [change 908220](https://gerrit.wikimedia.org/r/c/performance/docroot/+/908220) last week, we no longer display Coal metrics on the <https://performance.wikimedia.org/> homepage.
For monitoring, we now use Grafana alerts (done).
For the homepage, we now embed Grafana panels (done).
For long-term stability we are transitioning to Prometheus (not a blocker, in progress: T175087).
### Work
* [ ] De-provision `coal` and `coal-web` services in Puppet from webperf hosts in Beta Cluster, Eqiad, and Codfw.
* [ ] De-provision `coal` configuration in Puppet for Scap deployments.
* [ ] Remove unused Puppet code relating to coal, coal-web, and the coal Scap target.
* [ ] Remove unused Hieradata in Puppet (for prod) and in Horizon (for Beta Cluster) relating to coal.
* [ ] Archive the `performance/coal.git` repository.
* [ ] Update Wikitech runbooks and documentation.