Update dependency phpunit/phpunit to ^12.1.6

| datasource | package         | from   | to     |
| ---------- | --------------- | ------ | ------ |
| packagist  | phpunit/phpunit | 12.1.5 | 12.1.6 |

Author: renovate[bot]

composer.json

@@ -18,7 +18,7 @@
     "require-dev": {
         "phpstan/phpstan": "^2.1.16",
         "phpstan/phpstan-phpunit": "^2.0.6",
-        "phpunit/phpunit": "^12.1.5"
+        "phpunit/phpunit": "^12.1.6"
     },
     "autoload": {
         "psr-4": {