bug#25168: 25.1; variable-pitch face misbehaves

[Eli Zaretskii]

> From: Eli Barzilay <eli@barzilay.org>
> Date: Sat, 6 Feb 2021 07:22:41 -0500
> Cc: Eli Zaretskii <eliz@gnu.org>, 25168@debbugs.gnu.org
> 
> It would be nice to clarify that in the `text-scale-adjust` docstring.
> To be more specific, it currently repeats:
> 
>     the default face height
> 
> many times, and this can be interpreted as "the default (face height)"
> or "the (default face) height".  Worse, for people who don't know that
> there's an actual face called default, "Adjust the height of the default
> face" is just as confusing.

I made it say "adjust the height of the default face" because I think
it should be clear (or at least more clear than the original wording).