Doc: refer to array properly (#1541)

Author: stephenplusplus

packages/compute/src/region.js

@@ -672,8 +672,8 @@ Region.prototype.getRules = function(options, callback) {
  *     representing part of the larger set of results to view.
  * @param {function} callback - The callback function.
  * @param {?error} callback.err - An error returned while making this request.
- * @param {module:compute/subnetworks} callback.subnetworks - Subnetwork objects
- *     from this region.
+ * @param {module:compute/subnetwork[]} callback.subnetworks - Subnetwork
+ *     objects from this region.
  * @param {?object} callback.nextQuery - If present, query with this object to
  *     check for more results.
  * @param {object} callback.apiResponse - The full API response.