bug#33528: 26.1; doc string of `read-answer-short'

[Drew Adams]

1. Typo: `y-or-on-p' should be `y-or-n-p'.

2. Suggest you put the non-nil descriptions together, instead of the
   order `t', then `nil', then `auto'.  And start each on its own line.
   E.g.:

      Non-nil means `read-answer' accepts single-character answers.
      If nil...
      If t...
      If `auto'...

In GNU Emacs 26.1.90 (build 1, x86_64-w64-mingw32)
 of 2018-11-21
Repository revision: 7851ae8b443c62a41ea4f4440512aa56cc87b9b7
Windowing system distributor `Microsoft Corp.', version 10.0.16299
Configured using:
 `configure --without-dbus --host=x86_64-w64-mingw32
 --without-compress-install 'CFLAGS=-O2 -static -g3''