Automatic merge from submit-queue
Rbac api group make subject apiversion optional
This fixes the verification for the "apiVerion" field in the RBAC subject and makes it optional. This field isn't used and currently won't pass validation if it's filled.
```yml
kind: ClusterRoleBinding
apiVersion: rbac.authorization.k8s.io/v1alpha1
metadata:
name: admins
subject:
- kind: User
name: admin-user
# apiVersion: "entering anything here will fail validation"
roleRef:
kind: ClusterRole
name: admin
apiVersion: rbac.authorization.k8s.io/v1alpha1
```
1a23da5f6d