Coding Standards: Explicitly return null in wp_set_all_user_settings().

This matches the documented `@return` type.

Follow-up to [22256], [37263], [39932], [48320].

Props justlevine.
See #63268.
Built from https://develop.svn.wordpress.org/trunk@60361


git-svn-id: http://core.svn.wordpress.org/trunk@59697 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/option.php

@@ -1880,7 +1880,7 @@ function wp_set_all_user_settings( $user_settings ) {
 	}
 
 	if ( ! is_user_member_of_blog() ) {
-		return;
+		return null;
 	}
 
 	$settings = '';

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.9-alpha-60360';
+$wp_version = '6.9-alpha-60361';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.