Docs: Add @staticvar entries for $cache and $tested_paths in wp_upload_dir().

Props ajayghaghretiya1.
Fixes #41395.

git-svn-id: https://develop.svn.wordpress.org/trunk@41113 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.php

@@ -1856,6 +1856,9 @@ function wp_get_upload_dir() {
  * @since 2.0.0
  * @uses _wp_upload_dir()
  *
+ * @staticvar array $cache
+ * @staticvar array $tested_paths
+ *
  * @param string $time Optional. Time formatted in 'yyyy/mm'. Default null.
  * @param bool   $create_dir Optional. Whether to check and create the uploads directory.
  *                           Default true for backward compatibility.