Merge from origin/emacs-29

d58d0fa52ff Introduce 'let' using lexical binding in the Lisp Introdu...
1b123972636 ; Don't record multiple versions of use-package
8729a2a10d9 Fix 'rmail-summary-by-thread'
2a8c00bfc07 * doc/emacs/back.texi: Fix a typo.

diff --cc lisp/mail/rmailsum.el
Simple merge

diff --cc lisp/use-package/use-package-ensure-system-package.el
index 025721746cc66c3075c002a01e00615f65bbf371,3e369d996240718893aee5ae2d3593a22375df9b..6c7f8c0a1eade7ac2ace4a9fc0657e0340793e47
--- 1/lisp/use-package/use-package-ensure-system-package.el
--- 2/lisp/use-package/use-package-ensure-system-package.el
+++ b/lisp/use-package/use-package-ensure-system-package.el
@@@ -5,9 -5,9 +5,8 @@@
  ;; Author: Justin Talbott <justin@waymondo.com>
  ;; Keywords: convenience, tools, extensions
  ;; URL: https://github.com/waymondo/use-package-ensure-system-package
- ;; Version: 0.2
  ;; Package-Requires: ((use-package "2.1") (system-packages "1.0.4"))
  ;; Filename: use-package-ensure-system-package.el
 -;; Package: use-package
  
  ;; This file is part of GNU Emacs.