Update Javadoc for perimeterIrregularPolygon method

[vardhan30016]

Fixed incorrect @return description in perimeterIrregularPolygon method javadoc. Changed "trapezoid" to "irregular polygon" to accurately reflect what the method calculates.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.50%. Comparing base (a14e1e3) to head (d32f5fa).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7141      +/-   ##
============================================
- Coverage     78.51%   78.50%   -0.01%     
  Complexity     6752     6752              
============================================
  Files           759      759              
  Lines         22402    22402              
  Branches       4400     4400              
============================================
- Hits          17589    17587       -2     
- Misses         4108     4109       +1     
- Partials        705      706       +1     

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