test: remove redundant additional url tests

url-tests-additional.js now is a placeholder since existing test cases
have been upstreamed. This is now a temporary place for test cases
not upstreamed yet.

Refs: https://github.com/w3c/web-platform-tests/pull/4693
PR-URL: https://github.com/nodejs/node/pull/11439


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>