Upgrade deprecated Grafana Helm chart to grafana-community/grafana

[LakshmiSravyaVedantham]

Summary

The grafana/grafana Helm chart from https://grafana.github.io/helm-charts was deprecated on January 30, 2026. This PR migrates to the new grafana-community/grafana chart.

Changes

• build/Makefile: Update helm repo add URL from grafana.github.io/helm-charts to grafana-community.github.io/helm-charts, and chart reference from grafana/grafana to grafana-community/grafana
• site/content/en/docs/Guides/metrics.md: Update Grafana installation docs with new repo URL and chart name
• build/docs/make-reference.md: Update chart link to new URL

Not changed

• build/grafana.yaml and build/grafana-frontend.yaml: Our current values (service port, tolerations, affinity, sidecar dashboards, plugins, datasources) should be compatible with the new chart. The uninstall-grafana target also does not need changes since it references the release name, not the chart.

Closes #4447

Test plan

• make setup-grafana installs Grafana without the deprecation warning
• Dashboards load correctly in the Grafana UI
• make uninstall-grafana still works as expected

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[markmandel]

Will take this for a spin - but first we need the CLA signed please!

/gcbrun

[agones-bot]

Build Succeeded 🥳

Build Id: 6f2a87d1-036c-459f-a731-48df9f765b07

The following development artifacts have been built, and will exist for the next 30 days:

• image: us-docker.pkg.dev/agones-images/ci/agones-controller:1.56.0-dev-a3344cd
• image: us-docker.pkg.dev/agones-images/ci/agones-extensions:1.56.0-dev-a3344cd
• image: us-docker.pkg.dev/agones-images/ci/agones-sdk:1.56.0-dev-a3344cd-linux
• image: us-docker.pkg.dev/agones-images/ci/agones-ping:1.56.0-dev-a3344cd
• image: us-docker.pkg.dev/agones-images/ci/agones-allocator:1.56.0-dev-a3344cd
• image: us-docker.pkg.dev/agones-images/ci/agones-processor:1.56.0-dev-a3344cd
• Linux C++ SDK (build): agonessdk-1.56.0-dev-a3344cd-linux-arch_64.tar.gz
• SDK Server: agonessdk-server-1.56.0-dev-a3344cd.zip

A preview of the website (the last 30 builds are retained):

• https://a3344cd-dot-preview-dot-agones-images.appspot.com/

To install this version:

git fetch https://github.com/googleforgames/agones.git pull/4449/head:pr_4449 && git checkout pr_4449
helm install agones ./install/helm/agones --namespace agones-system --set agones.image.registry=us-docker.pkg.dev/agones-images/ci --set agones.image.tag=1.56.0-dev-a3344cd

[markmandel]

@LakshmiSravyaVedantham just checking in - would be great if you could sign the CLA, then we can merge the code 👍🏻