Update dependency phpunit/phpunit to v9.5.21

Author: renovate[bot]

composer.json

@@ -26,7 +26,7 @@
         "laravel/sail": "1.14.10",
         "mockery/mockery": "1.5.0",
         "nunomaduro/collision": "5.11.0",
-        "phpunit/phpunit": "9.5.20",
+        "phpunit/phpunit": "9.5.21",
         "squizlabs/php_codesniffer": "3.7.0"
     },
     "config": {