docs: fix jsdoc markup for array of arrays

dox wasn't parsing the last type.

lib/storage/file.js

@@ -781,18 +781,18 @@ File.prototype.getMetadata = function(callback) {
  * @param {object} options - Configuration object.
  * @param {object} options.expiration - Timestamp (seconds since epoch) when
  *     this policy will expire.
- * @param {object[][]=} options.equals - Array of request parameters and their
- *     expected value (e.g. [['$<field>', '<value>']]). Values are translated
- *     into equality constraints in the conditions field of the policy document
- *     (e.g. ['eq', '$<field>', '<value>']). If only one equality condition is
- *     to be specified, options.equals can be a one-dimensional array (e.g.
- *     ['$<field>', '<value>']).
- * @param {object[][]=} options.startsWith - Array of request parameters and
+ * @param {array|array[]=} options.equals - Array of request parameters and
+ *     their expected value (e.g. [['$<field>', '<value>']]). Values are
+ *     translated into equality constraints in the conditions field of the
+ *     policy document (e.g. ['eq', '$<field>', '<value>']). If only one
+ *     equality condition is to be specified, options.equals can be a one-
+ *     dimensional array (e.g. ['$<field>', '<value>']).
+ * @param {array|array[]=} options.startsWith - Array of request parameters and
  *     their expected prefixes (e.g. [['$<field>', '<value>']). Values are
  *     translated into starts-with constraints in the conditions field of the
  *     policy document (e.g. ['starts-with', '$<field>', '<value>']). If only
- *     one prefix condition is to be specified, options.startsWith can be a
- *     one-dimensional array (e.g. ['$<field>', '<value>']).
+ *     one prefix condition is to be specified, options.startsWith can be a one-
+ *     dimensional array (e.g. ['$<field>', '<value>']).
  * @param {string=} options.acl - ACL for the object from possibly predefined
  *     ACLs.
  * @param {string=} options.successRedirect - The URL to which the user client