After version 4.3.0 of the WP Travel we have adopted the react frame. But if you guys want to switch back to the previous setting then you can use the filter below.

For using the filter you have to go through the child theme. To know how you can activate and use the child theme, please refer to below given link.

Child Theme

Example:add_filter( 'wp_travel_settings_react_enabled', function() {
    return false;
});