helm-guestbook example cleanup

[danielhelfand]

The helm-guestbook example works as expected using the following commands:

argocd app create helm-guestbook --repo https://github.com/argoproj/argocd-example-apps --path helm-guestbook --dest-name in-cluster --dest-namespace default 

argocd app sync helm-guestbook

kubectl port-forward svc/guestbook-helm-guestbook 8080:80 -n default

The example should provide some documentation on the above commands and should also illustrate something unique about argo-cd's helm support. Maybe the values-production.yaml file should be updated and used as part of the example or an update can be pushed to the values file to show the change synced in.