Remove Kubelet --network-plugin=cni flag

* Now that `docker-shim` is no longer used, the Kubelet flag
is no longer needed and will be removed in v1.24

bare-metal/flatcar-linux/kubernetes/cl/controller.yaml

@@ -101,7 +101,6 @@ systemd:
           --healthz-port=0 \
           --hostname-override=${domain_name} \
           --kubeconfig=/var/lib/kubelet/kubeconfig \
-          --network-plugin=cni \
           --node-labels=node.kubernetes.io/controller="true" \
           --pod-manifest-path=/etc/kubernetes/manifests \
           --read-only-port=0 \

bare-metal/flatcar-linux/kubernetes/cl/worker.yaml

@@ -76,7 +76,6 @@ systemd:
           --healthz-port=0 \
           --hostname-override=${domain_name} \
           --kubeconfig=/var/lib/kubelet/kubeconfig \
-          --network-plugin=cni \
           --node-labels=node.kubernetes.io/node \
           %{~ for label in compact(split(",", node_labels)) ~}
           --node-labels=${label} \