CSI doc change and remove the CSI feature verifier

[blackpiglet]

Thank you for contributing to Velero!

Please add a summary of your change

Does your change fix a particular issue?

Fixes #7651

Please indicate you've done the following:

• [x] Accepted the DCO. Commits without the DCO will delay acceptance.
• [ ] Created a changelog file or added /kind changelog-not-required as a comment on this pull request.
• [ ] Updated the corresponding documentation in site/content/docs/main.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 61.82%. Comparing base (f25c154) to head (59eeec2). Report is 4 commits behind head on main.

Files	Patch %	Lines
pkg/backup/actions/csi/volumesnapshot_action.go	0.00%	8 Missing :warning:
pkg/restore/actions/csi/volumesnapshot_action.go	0.00%	3 Missing :warning:
...estore/actions/csi/volumesnapshotcontent_action.go	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #7656 +/- ## ========================================== + Coverage 61.26% 61.82% +0.55% ========================================== Files 276 276 Lines 31338 24864 -6474 ========================================== - Hits 19200 15371 -3829 + Misses 10784 8134 -2650 - Partials 1354 1359 +5 ```

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