Add a missing kwargs forward in skeleton_label_spec

[SpecLad]

Motivation and context

How has this been tested?

Another test I'm writing depends on this.

Checklist

• I submit my changes into the develop branch
• I have created a changelog fragment
• [ ] I have updated the documentation accordingly
• [ ] I have added tests to cover my changes
• [ ] I have linked related issues (see GitHub docs)

License

• I submit my code changes under the same MIT License that covers the project.
  Feel free to contact the maintainers if that's a concern.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 73.91%. Comparing base (fb3bde4) to head (5fd6b20).
Report is 3 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #9087      +/-   ##
===========================================
- Coverage    73.91%   73.91%   -0.01%     
===========================================
  Files          428      428              
  Lines        44530    44530              
  Branches      3881     3881              
===========================================
- Hits         32915    32913       -2     
- Misses       11615    11617       +2     

Components	Coverage Δ
cvat-ui	77.43% <ø> (-0.01%)	⬇️
cvat-server	71.00% <0.00%> (ø)