Enhance comments & improve readability in `LongestCommonSubsequence.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 54.54%. Comparing base (3390273) to head (28e82e4).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5523      +/-   ##
============================================
+ Coverage     54.34%   54.54%   +0.20%     
- Complexity     3399     3413      +14     
============================================
  Files           535      535              
  Lines         15392    15383       -9     
  Branches       2936     2935       -1     
============================================
+ Hits           8365     8391      +26     
+ Misses         6675     6638      -37     
- Partials        352      354       +2     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[Hardvan]

I have removed the main function and added unit tests for the LCS algorithm.