Update task-tutorial-prereqs.md

## Description

Remove Katacoda playground reference 

## Why
Katacoda.com is now closed

Author: manfontan

content/en/includes/task-tutorial-prereqs.md

@@ -2,7 +2,6 @@ You need to have a Kubernetes cluster, and the kubectl command-line tool must
 be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a
 cluster, you can create one by using
 [minikube](https://minikube.sigs.k8s.io/docs/tutorials/multi_node/)
-or you can use one of these Kubernetes playgrounds:
+or you can use this Kubernetes playground:
 
-* [Katacoda](https://www.katacoda.com/courses/kubernetes/playground)
 * [Play with Kubernetes](http://labs.play-with-k8s.com/)