Add MANNEQUIN to GHCommentAuthorAssociation enum

[choichanhyeok]

Description

This PR introduces the MANNEQUIN value to the GHCommentAuthorAssociation enum. This change is necessary to handle the unclaimed user scenario, particularly in migrated repositories where the user's association with the repository is not defined.

This fixes #1716.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (40992f7) 80.16% compared to head (b7a4574) 80.41%.
Report is 17 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1753      +/-   ##
============================================
+ Coverage     80.16%   80.41%   +0.25%     
- Complexity     2301     2309       +8     
============================================
  Files           217      218       +1     
  Lines          6962     7016      +54     
  Branches        371      371              
============================================
+ Hits           5581     5642      +61     
+ Misses         1150     1141       -9     
- Partials        231      233       +2     

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[choichanhyeok]

Hello @bitwiseman,

I wanted to express my gratitude for your review of my PR and for the adjustment you made to the 'MANNEQUIN' field. It was a detail I overlooked, and your your helpful modification not only corrected it but also improved the overall quality of the code. Your guidance and attention to detail are greatly appreciated.

This experience has been a valuable lesson for me in terms of attention to detail and has motivated me to be more thorough in my future contributions.

Thank you again for your support and for maintaining such a high standard in the project.

[bitwiseman]

Thanks for contributing this PR!