The CI doesn't pass with jsdom 16.0.0 on master anymore

[sjrd]

• Failed Travis job that I relaunched today: https://travis-ci.org/github/scala-js/scala-js-env-jsdom-nodejs/builds/683855737
• Failed attempt at migrating to GitHub Actions: https://github.com/sjrd/scala-js-env-jsdom-nodejs/runs/2042067327

Thanks npm for your non-reproducible ecosystem.

(And no, we could not have used package-lock.json, because we test against different versions of jsdom, which each have their own dependencies, so we have to reinstall from scratch every time.)