Bump friendsofphp/php-cs-fixer from 2.15.0 to 2.15.1

Bumps [friendsofphp/php-cs-fixer](https://github.com/FriendsOfPHP/PHP-CS-Fixer) from 2.15.0 to 2.15.1.
- [Release notes](https://github.com/FriendsOfPHP/PHP-CS-Fixer/releases)
- [Changelog](https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/2.15/CHANGELOG.md)
- [Commits](PHP-CS-Fixer/PHP-CS-Fixer@v2.15.0...v2.15.1)