Issue #3515406: Wrong return type in Xss::attributes() docblock

Closes #3515406

core/lib/Drupal/Component/Utility/Xss.php

@@ -275,7 +275,7 @@ protected static function split($string, array $html_tags, $class) {
    * @param string $attributes
    *   The html attribute to process.
    *
-   * @return string
+   * @return array
    *   Cleaned up version of the HTML attributes.
    */
   protected static function attributes($attributes) {