Update phpunit/phpunit requirement from ^8.5|^9.5 to ^9.6.21

---
updated-dependencies:
- dependency-name: phpunit/phpunit
  dependency-type: direct:development
...

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

composer.json

@@ -19,7 +19,7 @@
 		"phpstan/phpstan-php-parser": "^1.1",
 		"phpstan/phpstan-phpunit": "^1.0",
 		"phpstan/phpstan-strict-rules": "^1.1",
-		"phpunit/phpunit": "^8.5|^9.5",
+		"phpunit/phpunit": "^9.6.21",
 		"symplify/easy-coding-standard": "^11.4",
 		"tomasvotruba/unused-public": "^0.3",
 		"vlucas/phpdotenv": "^5.4"