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

[Aiden Grossman via llvm-commits]

boomanaiden154 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
```

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