[Docs]: The v5 examples(codesandbox) React version issue

[tasawar-hussain]

Describe what's incorrect/missing in the documentation

The code sandbox examples(all) for the v5 docs are broken, as they seem to use the latest version of react.

https://v5.reactrouter.com/web/example/basic
https://v5.reactrouter.com/web/example/modal-gallery