COMP: Remove copy_n wrapper for standard std::copy

A previous patch failed to remove copy_n in
Modules/Compatibility/Deprecated/src/itkDICOMImageIO2.cxx

Change-Id: I34a98db89afbbb2277f4b000d6bf4482c37b5b18
Merge topic 'Replace_copy_n_with_copy'

4204b80 COMP: Remove copy_n wrapper for standard std::copy