Fix Vx_show_tooltip_timeout in ns build, too

* src/nsfns.m (Fx_show_tip): Respect Vx_show_tooltip_timeout here,
too.

src/nsfns.m

@@ -2862,9 +2862,8 @@ DEFUN ("x-show-tip", Fx_show_tip, Sx_show_tip, 1, 6, 0,
   str = SSDATA (string);
   f = decode_window_system_frame (frame);
   if (NILP (timeout))
-    timeout = make_fixnum (5);
-  else
-    CHECK_FIXNAT (timeout);
+    timeout = Vx_show_tooltip_timeout;
+  CHECK_FIXNAT (timeout);
 
   if (NILP (dx))
     dx = make_fixnum (5);