Improve comments in ActivitySelection.java

[Hardvan]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.28%. Comparing base (7f60d57) to head (3522e7d).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5485      +/-   ##
============================================
- Coverage     52.28%   52.28%   -0.01%     
  Complexity     3256     3256              
============================================
  Files           525      525              
  Lines         15185    15185              
  Branches       2887     2887              
============================================
- Hits           7940     7939       -1     
- Misses         6920     6921       +1     
  Partials        325      325              

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[siriak]

Looks good, thanks!

[Hardvan]

Thank you!