Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

update Mount propagation version in comment

**What this PR does / why we need it**:
Mount propagation feature was moved to beta in PR [#59252](https://github.com/kubernetes/kubernetes/pull/59252)， so update the comment.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #60657 

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```