net/http: update bundle

go install golang.org/x/tools/cmd/bundle@latest
go generate net/http

This fixes the longtest builders, which broke at CL 570156.

Change-Id: I85e6a1c20bd0080228400a561efd750342ae2d67
Reviewed-on: https://go-review.googlesource.com/c/go/+/570276
Reviewed-by: Damien Neil <[email protected]>
Auto-Submit: Russ Cox <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: rsc