Direct path import of h3-quinn in test

[alexanderkjall]

Here h3-quinn is pulled in by a path reference: https://github.com/hyperium/h3/blob/master/h3/src/tests/mod.rs#L8

This makes it hard to run the test-suite in Debian, as we don't layout the files in the exact same way as you do in this git repository.

Would it be possible to have this as a normal [dev-dependencies] instead?

[seanmonstar]

The comments right above it explain why it isn't currently a dev-dependency. 🤷‍♂️