Update friendsofphp/php-cs-fixer requirement from 2.18.3 to 2.18.4 (#69)

Updates the requirements on [friendsofphp/php-cs-fixer](https://github.com/FriendsOfPHP/PHP-CS-Fixer) to permit the latest version.
- [Release notes](https://github.com/FriendsOfPHP/PHP-CS-Fixer/releases)
- [Changelog](https://github.com/FriendsOfPHP/PHP-CS-Fixer/blob/2.18/CHANGELOG.md)
- [Commits](PHP-CS-Fixer/PHP-CS-Fixer@v2.18.3...v2.18.4)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

composer.json

@@ -27,7 +27,7 @@
     "require-dev": {
         "phpunit/phpunit": "^8.0",
         "phpstan/phpstan": "0.12.82",
-        "friendsofphp/php-cs-fixer": "2.18.3",
+        "friendsofphp/php-cs-fixer": "2.18.4",
         "maglnet/composer-require-checker": "^1.1.0 || ^2.0.0",
         "phpro/grumphp-shim": "^0.22.0 || ^1.1"
     },