test: skip internet for test-npm-install

Disabling any internet-required features (namely audit and
update-notifer) in order for the test to work without an internet
connection.

- Fixes: https://github.com/nodejs/node/issues/36895

PR-URL: https://github.com/nodejs/node/pull/36933
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Myles Borins <myles.borins@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-npm-install.js

@@ -42,6 +42,8 @@ const env = { ...process.env,
               PATH: path.dirname(process.execPath),
               NPM_CONFIG_PREFIX: path.join(npmSandbox, 'npm-prefix'),
               NPM_CONFIG_TMP: path.join(npmSandbox, 'npm-tmp'),
+              NPM_CONFIG_AUDIT: false,
+              NPM_CONFIG_UPDATE_NOTIFIER: false,
               HOME: homeDir,
 };