Update docs/cluster_spec.md

Co-authored-by: Ciprian Hacman <ciprianhacman@gmail.com>

docs/cluster_spec.md

@@ -937,10 +937,9 @@ spec:
 ## containerRuntime
 {{ kops_feature_table(kops_added_default='1.18', k8s_min='1.11') }}
 
-Alternative [container runtimes](https://kubernetes.io/docs/setup/production-environment/container-runtimes/) can be used to run Kubernetes. The default container runtime is [containerd](https://containerd.io/docs/).
+As of Kubernetes 1.20, the default [container runtime](https://kubernetes.io/docs/setup/production-environment/container-runtimes) is containerd. Previously, the default container runtime was Docker.
 
-Docker can still be selected but be aware that Kubernetes is deprecating support for the Docker runtime from version 1.20 and will be removed in a future release (currently planned for the 1.22 release in late 2021).
-@see [Don't Panic: Kubernetes and Docker](https://kubernetes.io/blog/2020/12/02/dont-panic-kubernetes-and-docker/)
+Docker can still be used as container runtime with Kubernetes 1.20+,  but be aware that Kubernetes is [deprecating](https://kubernetes.io/blog/2020/12/02/dont-panic-kubernetes-and-docker) support for it and will be removed in Kubernetes 1.22.
 
 ```yaml
 spec: