doc: document that module.evaluate fulfills as undefined

Fixes: https://github.com/nodejs/node/issues/37453


Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: https://github.com/nodejs/node/pull/37663


Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Darshan Sen <raisinten@gmail.com>