test: update test-npm to use test-npm-package.js

Deletes the old test-npm.sh script.

PR-URL: https://github.com/nodejs/node/pull/11540
Refs: https://github.com/nodejs/node/pull/7867


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>