Update dependency phpunit/phpunit to v12

| datasource | package         | from   | to     |
| ---------- | --------------- | ------ | ------ |
| packagist  | phpunit/phpunit | 9.6.20 | 12.5.6 |

Author: renovate[bot]

composer.json

@@ -15,7 +15,7 @@
     "require": {
         "php": "~8.1.0 || ~8.2.0",
         "ext-json": "*",
-        "phpunit/phpunit": "^9.6.20"
+        "phpunit/phpunit": "^12.5.6"
     },
     "config": {
         "allow-plugins": {