Use k8s 'wait' parameter instead of separate 'kubectl wait' task

[geerlingguy]

I think I may have originally worked on the example in chapter 4 when the wait parameter was not in Ansible core's k8s module, and so I elected to use a separate kubectl wait parameter to wait for the hello-k8s pods to be in 'Ready' state.

The wait parameter is simpler and should be used instead of the separate command invocation.