Update quic-go for Go 1.21 support

[anacrolix]

This blocks updating quic-go for flashlight and friends.

[myleshorton]

This overlaps with the changes here, but I think most importantly we can't just update quic here vs in quicwrapper if the goal is to upgrade quic on the client side...and that has to be tested to make sure it's actually compatible with http-proxy-lantern because we use our fork with things like BBR and performance metrics.

[noahlevenson]

I don't understand the full context of what's going on here. In particular, I don't understand what this means:

we can't just update quic here vs in quicwrapper if the goal is to upgrade quic on the client side

Is it very important for me to learn this stuff and figure this out now, or can it wait a little while?

My preference would be to put this on ice for a moment as we head into the beta. But if it's blocking some very important stuff I can dig into it?

[myleshorton]

Putting it on ice is fine. I think the intent is to allow us to update to the latest Go, but this is the least of our worries for that goal.

[noahlevenson]

This ultimately was addressed here: #207