bug#57499: Documentation bug in the docstring of set-face-attribute?

[Gregory Heytings]

> > Should this go to master or to emacs-28?
>
> To master, please.

Thanks, now done.

A last suggestion: I think the docstring of set-face-attribute would be 
even clearer with

call this function with FRAME set to t or nil, and the ATTRIBUTE's value 
set to `unspecified'.

or with

call this function with FRAME set to t (or nil), and the ATTRIBUTE's value 
set to `unspecified'.

Just as a reminder that nil "implies" t.