net/http: update bundled http2

Updates bundled http2 to x/net git rev ed066c81e7 for:

    http2: Revert a closed stream cannot receive data
    https://golang.org/cl/153977

Updates golang/go#28204

Change-Id: I0a489e4e8a581a107970199f64f0fa9281982efe
Reviewed-on: https://go-review.googlesource.com/c/159179


Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>