bug#48058: tab-width's docstring

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

> I propose the following text instead:
>
>   Distance between tab stops (for display of tab characters), in columns.
>
>   This controls the width of a TAB character on display.
>   The value should be a positive integer.
>   Note that this variable doesn't necessarily affect the size of the
>   indentation step, but if the major mode's indentation facility
>   inserts one or more TAB characters, this variable will affect the
>   indentation step as well, even if `indent-tabs-mode' is non-nil.

Perhaps we could divide the last sentence up to make it easier to read?

    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.