[release-branch.go1.13] net/http: update bundled http2 for memory leak fix

This re-runs go generate with x/net checked out at CL 198617 on the
release-branch.go1.13 branch for:

   [release-branch.go1.13] http2: fix memory leak in random write scheduler

Fixes golang/go#34636
Updates golang/go#33812

Change-Id: Ibce630c6c7ffe43ff760d2ad40b44731c07ba870
Reviewed-on: https://go-review.googlesource.com/c/go/+/198897


Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>