Docs: Clarify the return description for wp_create_user() to illustrate that a WP_Error object will be returned on failure.

Props jmayhak
Fixes #33321.


git-svn-id: https://develop.svn.wordpress.org/trunk@33725 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/user.php

@@ -2365,7 +2365,8 @@ All at ###SITENAME###
  * @param string $username The user's username.
  * @param string $password The user's password.
  * @param string $email    Optional. The user's email. Default empty.
- * @return int|WP_Error The new user's ID.
+ * @return int|WP_Error The newly created user's ID or a WP_Error object if the user could not
+ *                      be created.
  */
 function wp_create_user($username, $password, $email = '') {
 	$user_login = wp_slash( $username );