LightGBM

[ci] apply cpplint to cpp tests (#4092)

* Update chunked_array.hpp

* Update ChunkedArray_API_extensions.i

* Update StringArray.i

* apply cpplint to cpp tests

* Update test_chunked_array to please cpplint (#4121)

* Update test_chunked_array to please cpplint

* Simplify var name

* Add comment

Co-authored-by: Alberto Ferreira <AlbertoEAF@users.noreply.github.com>