other: lower the timer for multi-digit in dd times (#469)

Lowers the timer for multi-digit inputs in dd.

I'm going to eventually completely rewrite the input part for the entire application though, but this will do for now.

src/app.rs

@@ -881,7 +881,7 @@ impl App {
                 .delete_dialog_state
                 .last_number_press
                 .map_or(100, |ins| ins.elapsed().as_millis())
-                > 500
+                >= 400
             {
                 self.delete_dialog_state.keyboard_signal_select = 0;
             }