test: fix fs benchmark test

Add missing option "mode". Alphabetize options for easier maintenance.

PR-URL: https://github.com/nodejs/node/pull/29967


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>