gnu: emacs-gnus-desktop-notify: Fix version string.

* gnu/packages/emacs-xyz.scm (emacs-gnus-desktop-notify): Cleanup.
[version]: Convert it to the conventions established in the manual.

Change-Id: I23b7da579b9a88422915a908b1a43011ea16ba04

gnu/packages/emacs-xyz.scm

@@ -40124,17 +40124,18 @@ message.
       (license license:gpl2+))))
 
 (define-public emacs-gnus-desktop-notify
+  ;; No tagged releases; version taken from source code
+  (let ((commit "12d2a52c0340a6d822f23cf8bc3f4d929c2d8838")
+        (revision "0"))
     (package
       (name "emacs-gnus-desktop-notify")
-    ;; There is no version tag; use a MELPA style date corresponding to that
-    ;; of the last commit.
-    (version "20250616.0809")
+      (version (git-version "1.4" revision commit))
       (source
        (origin
          (method git-fetch)
          (uri (git-reference
                 (url "https://gitlab.com/wavexx/gnus-desktop-notify.el.git")
-             (commit "12d2a52c0340a6d822f23cf8bc3f4d929c2d8838")))
+                (commit commit)))
          (file-name (git-file-name name version))
          (sha256
           (base32 "15gs8j5z88yvbpxjx9760isdiv6rz43m11f38yp5xh8i79x2gzwp"))))
@@ -40155,7 +40156,7 @@ configuration snippet in your @file{~/.gnus.el} configuration file:
 The above causes Gnus to scan all configured groups every two hours when
 Emacs has been idle for one hour, with desktop notifications emitted for new
 messages received.")
-    (license license:gpl3+)))
+      (license license:gpl3+))))
 
 (define-public emacs-ox-epub
   (package