style: cleanup PascalTriangle

[vil02]

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Describe your change:

This PR adds missing tests and cleans-up the implementation of PascalTriangle.

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new JavaScript files are placed inside an existing directory.
• All filenames should use the UpperCamelCase (PascalCase) style. There should be no spaces in filenames.
  Example:UserProfile.js is allowed but userprofile.js,Userprofile.js,user-Profile.js,userProfile.js are not
• All new algorithms have a URL in their comments that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (6aaa376) 82.44% compared to head (760db43) 82.46%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1606      +/-   ##
==========================================
+ Coverage   82.44%   82.46%   +0.01%     
==========================================
  Files         377      377              
  Lines       19747    19745       -2     
  Branches     2884     2886       +2     
==========================================
+ Hits        16281    16282       +1     
+ Misses       3466     3463       -3     

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