Fix airflow on k8s operator manager role

[CandiedCode]

Updated RBAC for manger-role to address the following error:

The ClusterRole "airflow-on-k8s-operator-manager-role" is invalid:

• rules[0].apiGroups: Required value: resource rules must supply at least one api group
• rules[1].apiGroups: Required value: resource rules must supply at least one api group
• rules[2].apiGroups: Required value: resource rules must supply at least one api group
• rules[3].apiGroups: Required value: resource rules must supply at least one api group

You can recreate this by running this locally against 1.16 or 1.19 k8s cluster

kind create cluster --image=kindest/node:v1.16.15 --name airflow 

kustomize build . | kubectl apply -f-

Where kustomization.yaml is

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - git@github.com:apache/airflow-on-k8s-operator/config/default?ref=master