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

[Eli Zaretskii]

> From: Sebastian Urban <mrsebastianurban@gmail.com>
> Cc: 48504@debbugs.gnu.org
> Date: Wed, 19 May 2021 13:17:28 +0200
> 
> >>> We didn't yet introduce the Ctrl etc. notation at that place.
> >>
> >> What about "Control" instead of "Ctrl"?
> >
> > You mean, just capitalize what the text already says? no objections
> > here.
> 
> No, I mean to change this:
>     (which is ``control h and then t'')
> into this:
>     (hold down @key{Control} and type @kbd{h}, then let go of
>     @key{Control} and type @kbd{t})

That's awkward.  How about

  To run the tutorial, start Emacs and type @kbd{C-h t} (that is,
  press and hold Control, then type h, then release Control and type
  t).