style: include SS_SHOULD_BE_STATIC

[vil02]

Continuation of #5122.

• 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 2.22222% with 44 lines in your changes are missing coverage. Please review.

Project coverage is 38.70%. Comparing base (c42b1c9) to head (9d8dd4c).

Files	Patch %	Lines
...healgorithms/datastructures/trees/RedBlackBST.java	0.00%	44 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5198      +/-   ##
============================================
+ Coverage     38.68%   38.70%   +0.01%     
- Complexity     2383     2384       +1     
============================================
  Files           517      517              
  Lines         15405    15403       -2     
  Branches       2959     2960       +1     
============================================
+ Hits           5960     5961       +1     
+ Misses         9158     9156       -2     
+ Partials        287      286       -1     

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[BamaCharanChhandogi]

Looks good, thanks.