How to remove the metabox from edit screen?

Hello, i would like to remove completely the metabox from the WP edit screen in order to prevent being loaded, in functions.php i have written:

function remove_unwanted_metaboxes() {
    $screen = get_current_screen();
    if (!$screen) {
        return;
    }

    // OneSignal Push Notifications
    remove_meta_box('onesignal_metabox', $screen->id, 'normal');
}

add_action('add_meta_boxes', 'remove_unwanted_metaboxes', 20);

but it don’t works.

Thanks in advice.

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