The observability documentation's links - section 1.6.3.2, https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_management_for_kubernetes/2.13/html-single/observability/index#add-res-obs-cert, point to the observability documentation but this topic was moved to the new documentation , "securing clusters", https://docs.redhat.com/en/documentation/red_hat_advanced_cluster_management_for_kubernetes/2.13/html-single/secure_clusters/index#replacing-cert-alertmanager.

This is new as of 2.13.