ob-core: Do not use `temporary-file-directory' function

* lisp/ob-core.el (org-babel-temporary-stable-directory): Use
`temporary-file-directory' variable instead of function.  The function
returns value depending on the `default-directory' at Org startup time
thus creating unpredictable temporary babel locations that may
sometimes litter current directory.

Reported-by: bhrgunatha <bhrgunatha@gmail.com>
Link: https://orgmode.org/list/93b040e1-6dc6-487f-de89-a4cea9a560ff@gmail.com

lisp/ob-core.el

@@ -3277,7 +3277,7 @@ Emacs shutdown.")
       (while (or (not dir) (file-exists-p dir))
         (setq dir (expand-file-name
                    (format "babel-stable-%d" (random 1000))
-                   (temporary-file-directory))))
+                   temporary-file-directory)))
       (make-directory dir)
       dir))
   "Directory to hold temporary files created to execute code blocks.