fix: avoid infinite loop in SwapSort

[alxkm]

There was an issue where this sorting implementation could enter an infinite loop, such as in the test shouldAcceptWhenArrayWithDuplicateValueIsPassed.

The index variable was not being updated correctly.
The index may never reach len - 1 due to the flawed logic, leading to a potential infinite loop.

This fix addresses the issue and adds the missing test for this sorting algorithm.

Fixes #5249.

• 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 39.82%. Comparing base (308bdcf) to head (06770a2).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5248      +/-   ##
============================================
+ Coverage     39.69%   39.82%   +0.13%     
- Complexity     2430     2437       +7     
============================================
  Files           517      517              
  Lines         15492    15476      -16     
  Branches       2958     2958              
============================================
+ Hits           6149     6164      +15     
+ Misses         9053     9022      -31     
  Partials        290      290              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.