Kubernetes Dashboard should upgrade to v2.6.0+ to ensure its compatib…

…ility

Amazon EKS supportted version have major changes over years
- https://docs.aws.amazon.com/eks/latest/userguide/kubernetes-versions.html#kubernetes-release-calendar

but the version for Kubernetes Dashboard have not been update for years, last update was made on Jul 9, 2020.

    ----
    commit 822d941
    Date:   Thu, 9 Jul 2020 11:47:59 +0800
    ----

should consider to upgrade its version shown on documentation to ensure its
compatibility. Furthermore, eksworkshop is now pointing to v2.0.0, should be
upgraded as well.

- https://www.eksworkshop.com/beginner/040_dashboard/dashboard/

Additionally, v2.5.0 having the following bugs that we should avoid it.

- kubernetes/dashboard#6784
- kubernetes/dashboard#6784 (comment)
- kubernetes/dashboard#6800

content/920_cleanup/undeploy.md

@@ -24,7 +24,7 @@ cd ~/environment/ecsdemo-nodejs
 kubectl delete -f kubernetes/service.yaml
 kubectl delete -f kubernetes/deployment.yaml
 
-export DASHBOARD_VERSION="v2.0.0"
+export DASHBOARD_VERSION="v2.6.0"
 
 kubectl delete -f https://raw.githubusercontent.com/kubernetes/dashboard/${DASHBOARD_VERSION}/src/deploy/recommended/kubernetes-dashboard.yaml
 ```

content/beginner/040_dashboard/dashboard.md

@@ -10,7 +10,7 @@ instructions in [the official documentation](https://kubernetes.io/docs/tasks/ac
 We can deploy the dashboard with the following command:
 
 ```bash
-export DASHBOARD_VERSION="v2.0.0"
+export DASHBOARD_VERSION="v2.6.0"
 
 kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/${DASHBOARD_VERSION}/aio/deploy/recommended.yaml
 ```