fix:duplicate tag immutable registered

[NishchayRajput]

Description

Briefly describe what this pull request does and why the change is needed.
In root/tag/cmd.go Immutable subcommand was registered twice.

• Fixes [bug]: Duplicate Immutable Tag in 'harbor tag' #923

Type of Change

Please select the relevant type.

• Bug fix
• New feature
• Refactor
• Documentation update
• Chore / maintenance

Changes

• remove duplicate immutable tag from root/tag/cmd.go

[qcserestipy]

Thank you for your contribution, please fix the linting since the generated docs are not in sync anymore

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 8.51%. Comparing base (60ad0bd) to head (3f4edc6).
⚠️ Report is 161 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##             main    #924      +/-   ##
=========================================
- Coverage   10.99%   8.51%   -2.48%     
=========================================
  Files         173     288     +115     
  Lines        8671   14442    +5771     
=========================================
+ Hits          953    1230     +277     
- Misses       7612   13095    +5483     
- Partials      106     117      +11     

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[NishchayRajput]

Thank you for your contribution, please fix the linting since the generated docs are not in sync anymore

Done. Thanks.