bug#22107: 25.1; Wrong docstring for this-single-command-keys

[Eli Zaretskii]

> From: Stefan Monnier <monnier@IRO.UMontreal.CA>
> Cc: bruce.connor.am@gmail.com, rgm@gnu.org, 22107@debbugs.gnu.org
> Date: Thu, 10 Dec 2015 13:37:33 -0500
> 
> This said, the distinction between "this-single-command-keys" and
> "this-command-keys" is something which should disappear, IMNSHO.

Are we sure no one out there depends on that?  This is a very old
feature.