mu4e: silence emacs header cookie complaints

Update header-cookies to avoid emacs cookie complaints.

Fixes #2841

mu4e/mu4e-config.el.in

@@ -1,9 +1,17 @@
-;; auto-generated
+;;; mu4e-config.el --- configuration values -*- lexical-binding: t -*-
+
+;;; Commentary:
+
+;; Auto-generated configuration values
+
+;;; Code:
 
 (defconst mu4e-mu-version "@VERSION@"
-  "Required mu binary version; mu4e's version must agree with this.")
+  "Required mu binary version.
+mu4e's version must agree with this.")
 
 (defconst mu4e-doc-dir "@MU_DOC_DIR@"
-  "Mu4e's data-dir.")
+  "Directory for mu4e documentation.")
 
 (provide 'mu4e-config)
+;;; mu4e-config.el.in ends here

mu4e/mu4e-headers.el

@@ -1,4 +1,4 @@
-;;; mu4e-headers.el --- Message headers -*- lexical-binding: t; coding:utf-8 -*-
+;;; mu4e-headers.el --- Message headers -*- lexical-binding: t  -*-
 
 ;; Copyright (C) 2011-2025 Dirk-Jan C. Binnema
 

mu4e/mu4e.el

@@ -1,4 +1,4 @@
-;;; mu4e.el --- Mu4e, the mu mail user agent -*- lexical-binding: t -*-
+;;; mu4e.el ---  Mu-based mua for emacs -*- lexical-binding: t -*-
 
 ;; Copyright (C) 2011-2025 Dirk-Jan C. Binnema