react-test-renderer is deprecated

https://www.npmjs.com/package/react-test-renderer

It's been marked as deprecated since https://github.com/facebook/react/pull/28705 and the README now recommends, funnily enough, [`@testing-library/react`](https://testing-library.com/docs/react-testing-library/intro) instead. https://github.com/testing-library/react-testing-library