Remove code-generator from hack/update-3generated-crd.code.sh

[blackpiglet]

Thank you for contributing to Velero!

Please add a summary of your change

The pkg/generated directory was deleted in PR #8114, but when running make update command, the pkg/generated directory is still created.
The reason is the hack/update-3generated-crd.sh runs the code-generator.
Remove the code-generator.

Does your change fix a particular issue?

Fixes #(issue)

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 59.02%. Comparing base (6c3988e) to head (c040207).
Report is 6 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #8117    +/-   ##
========================================
  Coverage   59.01%   59.02%            
========================================
  Files         358      364     +6     
  Lines       30141    30272   +131     
========================================
+ Hits        17789    17867    +78     
- Misses      10912    10959    +47     
- Partials     1440     1446     +6     

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[blackpiglet]

There are still some files in the Velero repository that have comments including code-generator, but I think it's OK if we leave it as it is.

• velero/Makefile

  Line 175 in 8fde4a0

  @# because the Kubernetes code-generator tools require the project to

• velero/hack/verify-generated-crd-code.sh

  Line 24 in 8fde4a0

  # with code-generator `--verify-only` option which discards generated changes