refactor: BoyerMoore

[alxkm]

Class cleanup.
Readability improvements.

• 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

Attention: Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 47.92%. Comparing base (5f6510f) to head (9544423).

Files	Patch %	Lines
...main/java/com/thealgorithms/others/BoyerMoore.java	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5395      +/-   ##
============================================
- Coverage     47.94%   47.92%   -0.03%     
+ Complexity     2962     2961       -1     
============================================
  Files           524      524              
  Lines         15281    15280       -1     
  Branches       2903     2903              
============================================
- Hits           7327     7323       -4     
  Misses         7654     7654              
- Partials        300      303       +3     

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