Add a missing return description for wp_styles().

See [31194]. See #31888.


git-svn-id: https://develop.svn.wordpress.org/trunk@32041 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.wp-styles.php

@@ -15,7 +15,7 @@
  *
  * @since 4.2.0
  *
- * @return WP_Styles
+ * @return WP_Styles WP_Styles instance.
  */
 function wp_styles() {
 	global $wp_styles;