Cancel tooltip when mouse leaves viewport

(cherry picked from commit 807431c49a)

scene/main/viewport.cpp

@@ -544,6 +544,7 @@ void Viewport::_notification(int p_what) {
 			gui.mouse_in_viewport = false;
 			_drop_physics_mouseover();
 			_drop_mouse_over();
+			_gui_cancel_tooltip();
 			// When the mouse exits the viewport, we want to end mouse_over, but
 			// not mouse_focus, because, for example, we want to continue
 			// dragging a scrollbar even if the mouse has left the viewport.