Update source file encoding list

Update source file encoding list

Update admin/notes/unicode, along with coding system cookies in
other files, so that the two match each other better.
* admin/notes/unicode: lisp/language/ethio-util.el and
lisp/language/ethiopic.el also use utf-8-emacs.
* admin/notes/hydra, doc/misc/dbus.texi, doc/misc/org.texi:
* doc/misc/remember.texi, etc/refcards/cs-dired-ref.tex:
* etc/refcards/cs-refcard.tex, etc/refcards/cs-survival.tex:
* etc/refcards/sk-dired-ref.tex, etc/refcards/sk-refcard.tex:
* etc/refcards/sk-survival.tex:
Add "coding: utf-8" so that this file is not mishandled in a
Latin-1 or Big-5 locale.
* lisp/international/robin.el, lisp/org/ox-ascii.el:
Specify utf-8, not utf-8-emacs, as these are plain UTF-8 files.
* lisp/language/ethio-util.el: Fix trailer.