doc: use _can_ to describe actions in quic.md

Per Microsoft style guide:

> When ability is what you need to express, it's OK to use _can_ to
> describe actions or tasks that the reader or program is able to do.
> Use _might_ to express possibility. Don't use _may_, which might be
> interpreted as providing permission.

Refs: https://docs.microsoft.com/en-us/style-guide/a-z-word-list-term-collections/c/can-may
Refs: https://github.com/nodejs/node/pull/34353#issuecomment-659169228

PR-URL: https://github.com/nodejs/node/pull/34613


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gerhard Stöbich <deb2001-github@yahoo.de>