Update dependency phpunit/phpunit to v12

Author: renovate[bot]

composer.json

@@ -19,7 +19,7 @@
         "symfony/polyfill-php56": "^1.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.0|^5.0"
+        "phpunit/phpunit": "12.3.0"
     },
     "autoload": {
         "psr-4": {