vendor: update golang.org/x/net/dns/dnsmessage from upstream

Updates to x/net git rev 24dd378 for CL 100055

Fixes #10622
Updates #16218

Change-Id: I99e26da7b908b36585a0379d9381030c01819b54
Reviewed-on: https://go-review.googlesource.com/101278


Run-TryBot: Ian Gudger <igudger@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>