editors/emacs: Update to 29.3

Emacs 29.3 is an emergency bugfix release intended to fix several
security vulnerabilities. For details, refer to the Changelog.

Changelog: https://git.savannah.gnu.org/cgit/emacs.git/tree/etc/NEWS?h=emacs-29.3

Reviewed by:	jrm
Security:	f661184a-eb90-11ee-92fc-1c697a616631
Differential Revision:	<https://reviews.freebsd.org/D44492

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Co-authored-by: Joseph Mingrone <jrm@FreeBSD.org>