class-wc-widget-layered-nav.php#L215

rename-layered-string.php

<?php
/**
 * Change text strings
 *
 * @link http://codex.wordpress.org/Plugin_API/Filter_Reference/gettext
 * @link https://github.com/woothemes/woocommerce/blob/master/includes/widgets/class-wc-widget-layered-nav.php#L215
 * @link http://speakinginbytes.com/2013/10/gettext-filter-wordpress/
 */
function translate_string_strings( $translated_text, $text, $domain ) {
	switch ( $translated_text ) {
		case 'Any %s' :
			$translated_text = __( '%s', 'woocommerce' );
			break;
	}
	return $translated_text;
}
add_filter( 'gettext', 'translate_string_strings', 20, 3 );