Backpressure request ignored in fetch() in Undici

Undici is an HTTP/1.1 client, written from scratch for Node.js. In affected versions calling `fetch(url)` and not consuming the incoming body ((or consuming it very slowing) will lead to a memory leak. This issue has been addressed in version 6.6.1. Users are advised to upgrade. Users unable to upgrade should make sure to always consume the incoming body.