Fix DataDownload fails during restore for empty PVC workload

[qiuming-best]

Thank you for contributing to Velero!

Please add a summary of your change

Does your change fix a particular issue?

Fixes #(issue)
#7388
There's no need to check whether the folder is empty or not.

The logic here wants to be consistent with Restic when backing up empty.
but empty does not mean backup empty dir, For our velero scenario, it does not generate one empty snapshot with an empty dir for both using Kopia or Restic. so we need to remove the empty dir checking logic for the problem mentioned in #7388

Please indicate you've done the following:

• 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]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.65%. Comparing base (84c1eca) to head (74ffa50).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7521      +/-   ##
==========================================
- Coverage   61.67%   61.65%   -0.03%     
==========================================
  Files         263      263              
  Lines       28676    28680       +4     
==========================================
- Hits        17687    17682       -5     
- Misses       9744     9753       +9     
  Partials     1245     1245              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.