Docs: Various docblock corrections particularly relating to boolean types.

See #51800


git-svn-id: https://develop.svn.wordpress.org/trunk@49926 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/user.php

@@ -1537,7 +1537,7 @@ function sanitize_user_field( $field, $value, $user_id, $context ) {
  * @since 3.0.0
  *
  * @param object|WP_User $user User object or database row to be cached
- * @return bool|null Returns false on failure.
+ * @return false|void Returns false on failure.
  */
 function update_user_caches( $user ) {
 	if ( $user instanceof WP_User ) {