lisp/org.el: Make `org-load-hook' obsolete

* lisp/org.el (org-load-hook): Make obsolete in favor of
`with-eval-after-load'.

lisp/org.el

@@ -653,6 +653,8 @@ defined in org-duration.el.")
   "Hook that is run after org.el has been loaded."
   :group 'org
   :type 'hook)
+(make-obsolete-variable 'org-load-hook
+                        "use `with-eval-after-load' instead." "Org 9.5")
 
 (defcustom org-log-buffer-setup-hook nil
   "Hook that is run after an Org log buffer is created."