Help merging fix to http2 code

[Jared Newman]

Hey Gophers,

Github issue #40423 details an issue that can cause an http.Server running http2 to fail to return connection-level flow control which ultimately causes the connection to hang.

The fix to this issue is 1 line change (with 60 lines of tests), and has been submitted by a core Go net maintainer, Michael Fraenkel. I have cherry-picked the change to the code base in which I originally reproduced the issue, confirmed it fixes it, and have deployed it to my company's production environment. However, the CR has not been reviewed for 6 weeks (!!).

Is there any chance that someone could help review and merge this change? 

Cheers,

Jared.