Remove the note about not being able to use Emacs on 'split' SGML files,
as the use of a Local Variables sections makes this eminently possible.
This is one issue in the referenced PR, but the PRs not complete, so it
stays open.

PR: docs/16439
Submitted by: Karlheinz Eckmeier <Karlheinz.Eckmeier@t-online.de>