Fix Duplicate Results for Sub-Arrays Correctly Formatted

Given...

return [
'zadornovov'=>['zadornovov', 'zadornovoff',],
'zadornovov'=>['zadornovov', 'zadornovoff',],
'zaffer'=>'zaffre',
];

If you run the `findDuplicateArrayKeys()`, you'll get....

>['zadornovov
>['zadornovov

This is because the last bracket is trimmed because it *possibly could be* the last bracket of the entire array structure, i.e., array=[el1, el2];, etc.. This code is failing to detect the alternate possibility, array=[[el1, el2], [el3, el4]];. Update code to fully detect these.