net/http: regenerate h2_bundle.go

net/http: regenerate h2_bundle.go

The x/net version was updated in CL 493596; cmd/internal/moddeps
catches the skew, but only runs on the -longtest builders (because it
requires network access for the bundle tool and x/net dependency).

Change-Id: I48891d51aab23b2ca6f4484215438c60bd8c8c21
Reviewed-on: https://go-review.googlesource.com/c/go/+/493875
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>