test: fix require-deps-deprecation for installed deps

Test test-require-deps-deprecation.js was failing when user already had
node installed with acorn in require.resolve range.

Modified test to acknowledge the possibility and throw only if acorn is
found in the deps directory.

PR-URL: https://github.com/nodejs/node/pull/17848
Fixes: https://github.com/nodejs/node/issues/17148


Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>