This filter returns and empty string for the '/ bundle' text displayed within the ticket selector.

functions.php

<?php //Please do not include the opening php tag if you already have one

//Return an empty string for the 'bundle' text used within the ticket selector
function ee_tw_remove_bundle_text() {
  return '';
}
add_filter( 'FHEE__ticket_selector_chart_template__per_ticket_bundle_text', 'ee_tw_remove_bundle_text' );