pkg/certwatcher: mentions callback is available but it isn't

[ahmetb]

https://pkg.go.dev/sigs.k8s.io/controller-runtime@v0.12.3/pkg/certwatcher mentions in multiple places that it supports callbacks, but that doesn't seem to be implemented.
/kind bug
/area docs

[k8s-ci-robot]

@ahmetb: The label(s) area/docs cannot be applied, because the repository doesn't have them.

In response to this:

https://pkg.go.dev/sigs.k8s.io/controller-runtime@v0.12.3/pkg/certwatcher mentions in multiple places that it supports callbacks, but that doesn't seem to be implemented.
/kind bug
/area docs

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/lifecycle stale

[k8s-triage-robot]

The Kubernetes project currently lacks enough active contributors to adequately respond to all issues and PRs.

This bot triages issues and PRs according to the following rules:

• After 90d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, lifecycle/rotten is applied
• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

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/lifecycle rotten

[ahmetb]

/lifecycle frozen