Update dependency phpunit/phpunit to v9.6.23

Author: renovate[bot]

composer.json

@@ -23,7 +23,7 @@
         "ext-intl": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "7.5.20|9.5.0",
+        "phpunit/phpunit": "9.6.23",
         "sunrise/coding-standard": "1.0.0"
     },
     "autoload": {