bug#43944: 28.0.50; Update modus-operandi, modus-vivendi themes to v0.13.0

[Eli Zaretskii]

> From: Protesilaos Stavrou <info@protesilaos.com>
> Cc: Stefan Kangas <stefankangas@gmail.com>,  43944@debbugs.gnu.org
> Date: Fri, 16 Oct 2020 23:39:55 +0300
> 
> With regard to British English, there is more of it in the *.el files I
> shared: "colour" probably is the most common one.  Shall I prepare a
> patch?

Yes, please.

Note that I didn't change a couple of those UK English spellings where
they affected too many places, for example one node that is referenced
from many places.  If you could take care of that as well, it would be
perfect.

Thanks.