[llvm] [CI] Remove buildkite from metrics container (PR #143049)

[via llvm-commits]

cmtice wrote:

> If someone could run the following commands to ensure the container gets restarted, that would be great:
> 
> ```
> gcloud container clusters get-credentials llvm-premerge-cluster-us-central --location us-central1-a
> kubectl get pods -n metrics # copy and paste the pod name
> kubectl delete pod <metrics pod name> -n metrics
> ```

Have these been run by anybody else, or do they still need to be run?


https://github.com/llvm/llvm-project/pull/143049