org-list: Fix misleading docstring

* lisp/org-list.el (org-list-allow-alphabetical): Remove reference to
  unused VALUE.

lisp/org-list.el

@@ -228,8 +228,7 @@ counters like \"[@c]\" will be recognized.
 
 This variable needs to be set before org.el is loaded.  If you
 need to make a change while Emacs is running, use the customize
-interface or run the following code, where VALUE stands for the
-new value of the variable, after updating it:
+interface or run the following code after updating it:
 
   \(when (featurep 'org-element) (load \"org-element\" t t))"
   :group 'org-plain-lists