Fix documentation references to the encode_mask SDK function

[SpecLad]

Motivation and context

How has this been tested?

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

All modified and coverable lines are covered by tests ✅

Project coverage is 73.40%. Comparing base (9d563bc) to head (f2b8a51).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #9013      +/-   ##
===========================================
- Coverage    73.41%   73.40%   -0.02%     
===========================================
  Files          416      416              
  Lines        44198    44198              
  Branches      3860     3860              
===========================================
- Hits         32447    32442       -5     
- Misses       11751    11756       +5     

Components	Coverage Δ
cvat-ui	77.37% <ø> (-0.03%)	⬇️
cvat-server	70.09% <ø> (ø)