Update Combination.java

[sarthakshelar07]

The updated code corrects the documentation, simplifies and clarifies the backtracking logic, avoids in-place mutation of the combination set by using a LinkedList during recursion, and constructs new TreeSet instances only for final results to ensure uniqueness and sorted order.

• 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

[sarthakshelar07]

The updated code corrects the documentation, simplifies and clarifies the backtracking logic, avoids in-place mutation of the combination set by using a LinkedList during recursion, and constructs new TreeSet instances only for final results to ensure uniqueness and sorted order.

[siriak]

The code looks good, please fix PR checks

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.15%. Comparing base (981d73d) to head (b8746af).
Report is 7 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6320      +/-   ##
============================================
- Coverage     74.16%   74.15%   -0.02%     
+ Complexity     5362     5359       -3     
============================================
  Files           678      678              
  Lines         18686    18681       -5     
  Branches       3625     3623       -2     
============================================
- Hits          13858    13852       -6     
  Misses         4273     4273              
- Partials        555      556       +1     

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