Mark echistory.el as obsolete

* lisp/obsolete/echistory.el: Add Obsolete-since header.
* etc/TODO: Delete echistory.
* etc/NEWS: Announce above obsoletion.  (Bug#76506)

etc/NEWS

@@ -1356,6 +1356,9 @@ behavior, customize the value of 'tooltip-delay' to zero.
 *** cdl.el is now obsolete.
 Use 'shell-command' and 'shell-command-on-region' instead.
 
+---
+*** echistory.el is now obsolete.
+
 ---
 *** hashcash.el is now obsolete.
 It is believed to no longer be useful as a method to fight spam.

etc/TODO

@@ -860,7 +860,7 @@ for completeness, but some may be worth documenting.
 
 Here's a list which is probably not complete/correct: align, allout,
 artist, ansi-color, array, calculator, cdl, cmuscheme, completion,
-delim-col, dirtrack, double, echistory, elide-head, easymenu, expand,
+delim-col, dirtrack, double, elide-head, easymenu, expand,
 flow-ctrl, format [format-alist], generic/generic-x [various modes],
 kermit, log-edit, makesum, midnight [other than in Kill Buffer node],
 mouse-copy [?], mouse-drag, mouse-sel, net-utils, snmp-mode

lisp/obsolete/echistory.el

@@ -4,6 +4,7 @@
 
 ;; Author: K. Shane Hartman
 ;; Maintainer: emacs-devel@gnu.org
+;; Obsolete-since: 31.1
 
 ;; This file is part of GNU Emacs.