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