bug#15917: 24.3.50; manual: mention keys reserved for users

[Eli Zaretskii]

> Date: Fri, 30 Oct 2020 13:50:28 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: stefan@marxist.se, michael_heerdegen@web.de, larsi@gnus.org,
>         15917@debbugs.gnu.org, psmith@gnu.org
> 
> > > Perhaps "GNU coding convention" would be even clearer than
> > > "GNU convention."
> > 
> > It is wrong to speak about GNU (coding) conventions here, since this
> > is not about GNU or coding, this is about key bindings in Emacs, and
> > in Emacs alone.
> 
> Sure.  If you think that wasn't clear enough then
> "GNU Emacs coding convention".  Or "Emacs Lisp
> coding convention".  Or "GNU Emacs Lisp coding
> convention".

None of the above fits, because these are not coding conventions.

We have a good text proposed already, let's not waste any more time
trying to make it better.