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

[Sebastian Urban]

>> 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.

What exactly? It's basically copy-paste from SCREEN.TEXI (L126). Is it
awkward there as well?

> 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).

Why @kbd/@key (commands for indication) can't be used here for
"Control"/"h"/"t"?

The complete sentence would look (in EMACS.TEXI) like this:

   To run the tutorial, start Emacs and type @kbd{C-h t} (that/which
   is, hold down @key{Control} and type @kbd{h}, then let go of
   @key{Control} and type @kbd{t}).

Whether there will be "that is" or "which is" - it's up to you.