Remove containerd_runtimes var in k8s-cluster.yml (kubernetes-sigs#7476)

Also set in all/containerd.yml

inventory/sample/group_vars/k8s-cluster/k8s-cluster.yml

@@ -197,18 +197,6 @@ container_manager: docker
 # Additional container runtimes
 kata_containers_enabled: false
 
-## Settings for containerd runtimes (only used when container_manager is set to containerd)
-# containerd_runtimes:
-#  - name: runc
-#    type: "io.containerd.runc.v2"
-#    engine: ""
-#    root: ""
-# Example for Kata Containers as additional runtime:
-#  - name: kata
-#    type: io.containerd.kata.v2
-#    engine: ""
-#    root: ""
-
 kubeadm_certificate_key: "{{ lookup('password', credentials_dir + '/kubeadm_certificate_key.creds length=64 chars=hexdigits') | lower }}"
 
 # K8s image pull policy (imagePullPolicy)