Update squizlabs/php_codesniffer requirement from ^3.7 to ^3.8

Updates the requirements on [squizlabs/php_codesniffer](https://github.com/PHPCSStandards/PHP_CodeSniffer) to permit the latest version.
- [Release notes](https://github.com/PHPCSStandards/PHP_CodeSniffer/releases)
- [Changelog](https://github.com/PHPCSStandards/PHP_CodeSniffer/blob/master/CHANGELOG.md)
- [Commits](PHPCSStandards/PHP_CodeSniffer@3.7.0...3.8.1)

---
updated-dependencies:
- dependency-name: squizlabs/php_codesniffer
  dependency-type: direct:development
...

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

composer.json

@@ -14,7 +14,7 @@
     "require-dev": {
         "php-di/php-di": "^7.0",
         "phpunit/phpunit": "^9.6",
-        "squizlabs/php_codesniffer": "^3.7",
+        "squizlabs/php_codesniffer": "^3.8",
         "vimeo/psalm": "^5.7"
     },