test: use faster variant for rss in test-vm-memleak.js

PR-URL: https://github.com/nodejs/node/pull/36769
Refs: https://github.com/nodejs/node/pull/34291


Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>