Update MaximumSumOfNonAdjacentElements.java

[MahaleHarsh]

Added handling for single-element arrays. Made the take calculation more concise. Kept the variable update logic the same but provided better explanations. Improved comment clarity and consistency.

• [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 66.72%. Comparing base (169a01e) to head (55199ea).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5874      +/-   ##
============================================
- Coverage     66.74%   66.72%   -0.02%     
  Complexity     4489     4489              
============================================
  Files           610      610              
  Lines         16929    16928       -1     
  Branches       3267     3268       +1     
============================================
- Hits          11299    11296       -3     
- Misses         5182     5183       +1     
- Partials        448      449       +1     

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[siriak]

Please add corresponding JUnit tests and fix PR checks

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