org-agenda: Small refactoring

* lisp/org-agenda.el (org-agenda-deadline-face): Small refactoring.

lisp/org-agenda.el

@@ -6185,10 +6185,7 @@ specification like [h]h:mm."
 (defun org-agenda-deadline-face (fraction)
   "Return the face to displaying a deadline item.
 FRACTION is what fraction of the head-warning time has passed."
-  (let ((faces org-agenda-deadline-faces) f)
-    (catch 'exit
-      (while (setq f (pop faces))
-	(if (>= fraction (car f)) (throw 'exit (cdr f)))))))
+  (assoc-default fraction org-agenda-deadline-faces #'<=))
 
 (defun org-agenda-get-scheduled (&optional deadlines with-hour)
   "Return the scheduled information for agenda display.