The rbac.authorization.k8s.io/v1beta1 API was deprecated and replaced
with rbac.authorization.k8s.io/v1. Version 1.22.0 of Kuberenetes removes
the deprecated API which means Nodepool needs to stop using it.
According to the docs [0] version 1.8 and newer support the new APIs.
To address this we update our RBAC client instance to use the non beta
version client and update our version specification in the manifests to
drop the beta version.
Add a release note indicating that K8s 1.8 and newer is now required.
Additionally we unpin minikube in testing to ensure we have test
coverage of this change against newer Kuberentes.
[0] https://kubernetes.io/docs/reference/using-api/deprecation-guide/#rbac-resources-v122
Story: 2009974
Change-Id: Ic21725efc8088e7dfb0777c2c96c742182cdbf93
046a7da086