breadcrumbs-list.php

/**
 * Filter the output of Yoast breadcrumbs to remove <span> tags added by the plugin
 * @param $output
 *
 * @return mixed
 */
function j_filter_yoast_breadcrumb_output( $output ){

	$from = '<span>';
	$to = '</span>';
	$output = str_replace( $from, $to, $output );

	return $output;
}
add_filter( 'wpseo_breadcrumb_output', 'j_filter_yoast_breadcrumb_output' );