minor doc fix

Author: sanfilip

lib/machines/utilization.js

@@ -11,7 +11,7 @@ var assign = require('lodash.assign');
  * @param {string} params.machineId - Id of the machine to get utilization data for
  * @param {string} params.billingMonth - Billing period to query in `YYYY-MM` format
  * @param {function} cb - Node-style error-first callback function
- * @returns {object} machine - The utilization JSON object
+ * @returns {object} utilization - The utilization JSON object
  * @example
  * paperspace.machines.utilization({
  *   machineId: 'ps123abc',