[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 #34636
Updates #33812

Change-Id: Ibce630c6c7ffe43ff760d2ad40b44731c07ba870
Reviewed-on: https://go-review.googlesource.com/c/go/+/198897
Run-TryBot: Brad Fitzpatrick <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Bryan C. Mills <[email protected]>

Author: bradfitz