benchmark: fix bench-mkdirp to use recursive option

The original PR didn't update the benchmark after renaming the option.

PR-URL: https://github.com/nodejs/node/pull/23699


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>