Update dependency phpunit/phpunit to ^9.6.6 (#338)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

composer.json

@@ -31,7 +31,7 @@
     "phpstan/phpstan-deprecation-rules": "^1.1.3",
     "phpstan/phpstan-phpunit": "^1.3.11",
     "phpstan/phpstan-strict-rules": "^1.5.0",
-    "phpunit/phpunit": "^9.6.5",
+    "phpunit/phpunit": "^9.6.6",
     "rector/rector": "^0.15.23"
   },
   "config": {