bug#32578: Remove "joke" from drag events documentation

[Eli Zaretskii]

tags 32578 wontfix
thanks

> From: Richard Stallman <rms@gnu.org>
> Date: Thu, 30 Aug 2018 21:23:24 -0400
> Cc: 32578@debbugs.gnu.org
> 
> We will keep that joke, because there is nothing wrong with it.  The
> joke is not unwelcoming to anyone, and does not exclude anyone.  In
> the GNU Project, we appreciate the occasional joke, and we do not aim
> for Victorian prudery.
> 
> Happy hacking.

By popular demand, I'm closing this bug as "wontfix".

Thanks.