Update dependency phpunit/phpunit to v12

Author: text-html-renovate[bot]

composer.json

@@ -13,7 +13,7 @@
         }
     ],
     "require-dev": {
-        "phpunit/phpunit": "^5.0|^6.0|^7.0|^8.0|^9.0|^10.5|^11.0"
+        "phpunit/phpunit": "12.0.1"
     },
     "require": {
         "ext-pcntl": "*",