Automatic merge from submit-queue
Remove 'beta' from default storage class annotation (storage/util)
**What this PR does / why we need it**:
This is a follow up to: #42991 where I believe this file was overlooked.
It removes `beta` from the default storageclass annotation.
Without this fix you are not able to specify a default storage class like this:
```yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: standard
annotations:
storageclass.kubernetes.io/is-default-class: "true"
provisioner: kubernetes.io/aws-ebs
parameters:
type: gp2
```
because the annotation is ignored in: https://github.com/kubernetes/kubernetes/blob/master/plugin/pkg/admission/storageclass/default/admission.go#L129
**Special notes for your reviewer**:
**Release note**:
```release-note
None
```
/cc @jsafrane
e2aa686a25