bug#27798: Documentation of locate-dominating-file is wrong

[Eli Zaretskii]

> Cc: 27798@debbugs.gnu.org
> From: Clément Pit--Claudel <clement.pitclaudel@live.com>
> Date: Sun, 23 Jul 2017 18:08:23 +0200
> 
> On 2017-07-23 17:20, Eli Zaretskii wrote:
> > It would probably be more accurate if we said
> > 
> >   FILE can be a directory.
> 
> Sounds good.  In that case we also need to adjust the part of the docstring 
> about NAME (when FILE is not a directory and NAME is a lambda, NAME is called 
> with something that's not a directory — namely FILE).

Done.