benchmark: fix net-wrap-js-stream-passthrough

The net-wrap-js-stream-passthrough benchmark was inadvertently broken by
00944c7c. This fixes it.

PR-URL: https://github.com/nodejs/node/pull/25273


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>