bug#30660: mention describe-bindings on (info "(emacs) Keymaps")

[Eli Zaretskii]

> From: Stefan Kangas <stefan@marxist.se>
> Cc: larsi@gnus.org,  30660@debbugs.gnu.org,  jidanni@jidanni.org
> Date: Sun, 17 Nov 2019 21:36:53 +0100
> 
> > I don't know why describe-bindings was documented in both manuals,
> > and see no reason to continue doing so (the ELisp manual prints in 2
> > large volumes, so avoiding any unnecessary bloat there is generally
> > a good idea).
> 
> Here's a separate patch to remove it, while preserving the information
> by moving it to the doc string of 'describe-bindings'.

Why move that to the doc string? why not to the user manual?