composer: update ergebnis/php-cs-fixer-config requirement

Updates the requirements on [ergebnis/php-cs-fixer-config](https://github.com/ergebnis/php-cs-fixer-config) to permit the latest version.
- [Release notes](https://github.com/ergebnis/php-cs-fixer-config/releases)
- [Changelog](https://github.com/ergebnis/php-cs-fixer-config/blob/6.56.0/CHANGELOG.md)
- [Commits](ergebnis/php-cs-fixer-config@6.55.0...6.56.0)

---
updated-dependencies:
- dependency-name: ergebnis/php-cs-fixer-config
  dependency-version: 6.56.0
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

composer.json

@@ -36,7 +36,7 @@
         "phpstan/phpstan": "*",
         "friendsofphp/php-cs-fixer": "^3.88",
         "ergebnis/composer-normalize": "^2.47",
-        "ergebnis/php-cs-fixer-config": "^6.55",
+        "ergebnis/php-cs-fixer-config": "^6.56",
         "phpstan/phpstan-phpunit": "^2.0"
     },
     "autoload": {