docu: improve roll calendar example (#96)

lib/steps/select.js

@@ -87,7 +87,7 @@ When('we select month {string}', async function( month ) {
 * @name When we roll calendar to {string}
 * @description Performs the specified action on the currently opened calendar.
 * @param {string} action action to perform on the calendar: "next month", "next year"
-* @example When we roll calendar to {string}
+* @example When we roll calendar to "next month"
 */
 When('we roll calendar to {string}', async function( action ) {
   await this.controller.rollVisibleCalendar(action);