win: rename find_toplevel2 to find_toplevel_nocache

So it is slightly clearer what is the difference to find_toplevel().

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/win.c

@@ -2195,7 +2195,7 @@ struct managed_win *find_toplevel(session_t *ps, xcb_window_t id) {
  * @param wid window ID
  * @return struct _win object of the found window, NULL if not found
  */
-struct managed_win *find_toplevel2(session_t *ps, xcb_window_t wid) {
+struct managed_win *find_toplevel_nocache(session_t *ps, xcb_window_t wid) {
 	// TODO this should probably be an "update tree", then find_toplevel.
 	//      current approach is a bit more "racy"
 	struct win *w = NULL;