remove internal `sorted-dirlist` function
remove internal `sorted-dirlist` function

The result of `directory-list` is now sorted by default, so the
extra function is not needed.

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket