bug#48504: Improve style of C-h t description (Preface)

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Wed, 29 Sep 2021 05:07:09 -0700
> Cc: Sebastian Urban <mrsebastianurban@gmail.com>, 48504@debbugs.gnu.org
> 
> >   To run the tutorial, start Emacs and type @kbd{C-h t} (that is,
> >   @kbd{Ctrl+H}, then @kbd{T}).

The first @kbd should be @kbd{@key{Ctrl} H}, I think.  For two
reasons:

  . "Ctrl" is a single key, not 4 characters C t r l
  . "+" isn't something the user should type

IOW, what you suggest violates our (and Texinfo's) conventions for
markup of key sequences.  Which is why I proposed a pure-English
description that doesn't use any fancy markup that could only confuse
at this point.

Question: what do we gain from using "Ctrl+H" instead?