bug#35361: 26.2; doc string of `read-buffer'

[Eli Zaretskii]

> Date: Sun, 21 Apr 2019 15:02:37 +0000 (UTC)
> From: Drew Adams <drew.adams@oracle.com>
> 
> The doc string does not tell you what the completion candidates are
> (they are apparently singleton conses with car a buffer name).  So
> it is impossible for a user to know what kind of PREDICATEs to define, 
> i.e., what kinds of completion candidates are to be accepted as arg
> and tested.

Thanks, fixed.