Improve comments in `SumOfSubset.java`

[Hardvan]

• [x] I have read CONTRIBUTING.md.
• [x] This pull request is all my own work -- I have not plagiarized it.
• [x] All filenames are in PascalCase.
• [x] All functions and variable names follow Java naming conventions.
• [x] All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• [x] 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 :white_check_mark:

Project coverage is 54.32%. Comparing base (ce34595) to head (4049e42).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5514      +/-   ##
============================================
- Coverage     54.33%   54.32%   -0.02%     
+ Complexity     3399     3398       -1     
============================================
  Files           535      535              
  Lines         15392    15392              
  Branches       2936     2936              
============================================
- Hits           8363     8361       -2     
- Misses         6676     6677       +1     
- Partials        353      354       +1     

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[Hardvan]

I have removed the extra comments in the function body.