test: refactor test-enable-in-init

Remove unused function arguments. Convert to ES6 arrow syntax.

PR-URL: https://github.com/nodejs/node/pull/24976


Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>