bug#48058: tab-width's docstring

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Date: Fri, 30 Apr 2021 05:20:12 -0500
> Cc: gusbrs.2016@gmail.com, 48058@debbugs.gnu.org
> 
>     Note that this variable doesn't necessarily affect the size of the
>     indentation step.  However, if the major mode's indentation facility
>     normally inserts one or more TAB characters, this variable will
>     affect the indentation step as well, even if `indent-tabs-mode' is
>     non-nil.
> 
> Otherwise LGTM, please install.

Thanks, done (with one minor deviation: the "normally" part is not
useful here).