Update slevomat/coding-standard requirement from ^6.4 to ^7.0

Updates the requirements on [slevomat/coding-standard](https://github.com/slevomat/coding-standard) to permit the latest version.
- [Release notes](https://github.com/slevomat/coding-standard/releases)
- [Commits](slevomat/coding-standard@6.4.0...7.0.0)

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

Author: dependabot-preview[bot]

composer.json

@@ -34,7 +34,7 @@
         "php-coveralls/php-coveralls" : "^2.2",
         "phpmd/phpmd": "^2.7",
         "phpunit/phpunit": "^9.0",
-        "slevomat/coding-standard": "^6.4",
+        "slevomat/coding-standard": "^7.0",
         "squizlabs/php_codesniffer": "^3.4",
         "symfony/thanks": "^1.2",
         "laravel/legacy-factories": "^1.0"