Backport commit c1145c31a from Emacs

* lisp/org-compat.el (file-attribute-modification-time):
Update doc string to match that of builtin Emacs.

Update org-compat doc string
c1145c31adf143460911dd87b408d35ea88a1a92
Paul Eggert
Sun Dec 5 23:24:10 2021 -0800

lisp/org-compat.el

@@ -204,8 +204,7 @@ extension beyond end of line was not controllable."
   (defsubst file-attribute-modification-time (attributes)
     "The modification time in ATTRIBUTES returned by `file-attributes'.
 This is the time of the last change to the file's contents, and
-is a list of integers (HIGH LOW USEC PSEC) in the same style
-as (current-time)."
+is a Lisp timestamp in the same style as `current-time'."
     (nth 5 attributes)))
 
 (unless (fboundp 'file-attribute-size)