Automatic merge from submit-queue
Make pvc storage class annotation immutable after create
Fixes#34516
Added immutable check in validation.go
```
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
# persistentvolumeclaims "gce-claim-storageclass" was not valid:
# * metadata.annotations.volume.beta.kubernetes.io/storage-class: Invalid value: "slow2": field is immutable
#
```
1b2a4b55bb