[media] Remove unneeded comments from the media API DocBook files

This removes comment tags intended for emacs configuration from
67 files in the Media API DocBook. Such comments are not really
helpful and violate  the coding style rules.

Signed-off-by: Sylwester Nawrocki <snjw23@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>