[en] Fix ClusterTrustBundle API reference link

[popsiclelmlm]

Summary

• Update the English Certificate Signing Requests page metadata for ClusterTrustBundle from certificates.k8s.io/v1alpha1 to certificates.k8s.io/v1beta1.
• This lets the page-api-reference shortcode resolve the existing ClusterTrustBundle API reference page instead of rendering %!s(<nil>).

Reproduction

On /docs/reference/access-authn-authz/certificate-signing-requests/#what-s-next, the "Read about the ClusterTrustBundle API" bullet rendered %!s(<nil>) instead of a link.

Root cause

The page front matter still pointed ClusterTrustBundle at certificates.k8s.io/v1alpha1, but the generated English API reference page is content/en/docs/reference/kubernetes-api/certificates/cluster-trust-bundle-v1beta1.md with apiVersion: "certificates.k8s.io/v1beta1". The shortcode builds API reference links by matching kind and apiVersion, so the stale metadata produced no map entry for ClusterTrustBundle.

Changes

• Change the English page api_metadata entry for ClusterTrustBundle to certificates.k8s.io/v1beta1.
• Remove trailing whitespace on that front matter line.
• Keep this PR scoped to the English page; the zh-cn page can be handled in a separate localization PR as suggested on the issue.

Tests

• awk 'prev ~ /apiVersion: "certificates.k8s.io\\/v1beta1"/ && $0 ~ /kind: "ClusterTrustBundle"/ {found=1} {prev=$0} END {if (!found) exit 1; print "page metadata points to ClusterTrustBundle v1beta1"}' content/en/docs/reference/access-authn-authz/certificate-signing-requests.md
• awk 'BEGIN{inmeta=0} /^---$/ {if (!inmeta) {inmeta=1; next} else {inmeta=0; exit}} inmeta && /apiVersion: "certificates.k8s.io\\/v1beta1"/ {version=1} inmeta && /kind: "ClusterTrustBundle"/ {kind=1} END {if (!(version && kind)) exit 1; print "API reference front matter is ClusterTrustBundle v1beta1"}' content/en/docs/reference/kubernetes-api/certificates/cluster-trust-bundle-v1beta1.md
• git diff --check origin/main..HEAD

Screenshots/Logs

• Not applicable; this is a front matter metadata fix.
• Local Hugo render was not run because hugo is not installed in this environment.

Issue

Related to #56092.

[k8s-ci-robot]

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[Arhell]

/lgtm

[Caesarsage]

Thank you for the contribution, @popsiclelmlm!

Did you use AI to generate these changes? If yes, project policy requires disclosing the tooling used in the PR description.

I'm asking because the Screenshots/Logs section suggests this wasn't built or tested locally before opening the PR, a common pattern with AI-generated submissions. Even for a small change, please set up your environment and verify the result; the contribution guide walks through the local setup.

Holding until the AI question is answered, anyone can /unhold and approve after that.

/lgtm cancel
/hold

[k8s-ci-robot]

PR needs rebase.

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