Emphasize emacs-29-specificity in this version of lisp/progmodes/eglot.el

Emphasize emacs-29-specificity in this version of lisp/progmodes/eglot.el

Do not merge to master.

Before working on bugfixes to Eglot in its non-ELPA form delivered
with Emacs 29, it's important to distinguish between this emacs-29
version and the one in master, which will also get the bugfixes (via
routine gitmerge.el) but with a bumped version number.

* lisp/progmodes/eglot.el (Version): Emphasize Emacs 29, but hint this
is 1.12 + something.
(Package-Requires): Remove.  Everything required is already in Emacs
29.