Omit edition numbers and dates in manuals

These seem to cause more confusion than they cure; e.g.,
https://shop.fsf.org/books/gnu-emacs-manual-18th-edition-v-261
currently advertises "18th edition" even as it points to
https://www.gnu.org/software/emacs/manual/pdf/emacs.pdf
which says "Seventeenth Edition".  It is simpler and less
confusing to stick to one version number like "26.3".  If we
need a separate edition number for each printed manual for
some reason (marketing?) we can put “@ifset printed-edition”
around anything specific to the printed editions.
(as opposed to online PDF copies).
* doc/emacs/emacs.texi (EDITION):
* doc/lispintro/emacs-lisp-intro.texi (edition-number, update-date):
* doc/lispref/elisp.texi (VERSION, DATE):
Remove, and remove uses.

doc/lispintro/emacs-lisp-intro.texi

@@ -63,10 +63,6 @@
 \global\hbadness=6666 % don't worry about not-too-underfull boxes
 @end tex
 
-@c These refer to the printed book sold by the FSF.
-@set edition-number 3.10
-@set update-date 28 October 2009
-
 @c For next or subsequent edition:
 @c   create function using with-output-to-temp-buffer
 @c   create a major mode, with keymaps
@@ -106,9 +102,6 @@
 This is @cite{An Introduction to Programming in Emacs Lisp}, for
 people who are not programmers.
 @sp 1
-@iftex
-Edition @value{edition-number}, @value{update-date}
-@end iftex
 @ifnottex
 Distributed with Emacs version @value{EMACSVER}.
 @end ifnottex