Docs: In various @return tags, list the expected type first, instead of WP_Error.

See #48303.

git-svn-id: https://develop.svn.wordpress.org/trunk@46696 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/wp-db.php

@@ -3499,7 +3499,7 @@ class wpdb {
 	 * @global string $wp_version
 	 * @global string $required_mysql_version
 	 *
-	 * @return WP_Error|void
+	 * @return void|WP_Error
 	 */
 	public function check_database_version() {
 		global $wp_version, $required_mysql_version;