test: fix misleading comment

The comment is outdated, function declarations have
nothing to do with defineProperties.

PR-URL: https://github.com/nodejs/node/pull/12048


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Yuta Hiroto <hello@about-hiroppy.com>
Reviewed-By: James M Snell <jasnell@gmail.com>