bug#35370: notmuch-emacs: avoiding deprecated message-default-charset

Tue May 7 07:36:37 PDT 2019

> From: Noam Postavsky <npostavs at gmail.com>
> Cc: Daniel Kahn Gillmor <dkg at fifthhorseman.net>,  david at tethera.net,  notmuch at notmuchmail.org,  35370 at debbugs.gnu.org
> Date: Tue, 07 May 2019 08:26:59 -0400
> 
> > Just remove any uses of it.  Why are you using it now?
> 
> Should we remove the remaining uses of it from Emacs too?

I think so, but I'd be happier if someone from the Gnus folks could
eyeball this patch.

Lars, any comments/objections?