New 404 link failures in advanced topics

[grokspawn]

References for validating/mutating webhooks in the advanced topics section have moved and are now rendering 404 failures. For e.g. https://github.com/operator-framework/olm-docs/actions/runs/5003938556/jobs/8965829290?pr=296

Link targets:

• https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.19/#mutatingwebhookconfiguration-v1-admissionregistration-k8s-io
• https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.19/#validatingwebhookconfiguration-v1-admissionregistration-k8s-io