Use this snippet to remove the "- optional" suffix displayed next to the title of optional bundled items.

woocommerce-bundles-remove-optional-suffix.php

<?php
/**
 * Plugin Name: WooCommerce Product Bundles - Remove Optional Suffix
 * Plugin URI: https://woocommerce.com/products/product-bundles/
 * Description: Use this snippet to remove the "- optional" suffix displayed next to the title of optional bundled items.
 * Version: 1.0
 * Author: SomewhereWarm
 * Author URI: https://somewherewarm.gr/
 * Developer: Manos Psychogyiopoulos
 *
 * Requires at least: 4.1
 * Tested up to: 5.3
 *
 * Copyright: © 2017-2020 SomewhereWarm SMPC ([email protected]).
 * License: GNU General Public License v3.0
 * License URI: http://www.gnu.org/licenses/gpl-3.0.html
 */
 
add_filter( 'woocommerce_bundles_optional_bundled_item_suffix', 'wc_pb_remove_optional_suffix', 10, 3 );

function wc_pb_remove_optional_suffix( $suffix, $bundled_item, $bundle ) {
	return '';
}