Update dependency phpunit/phpunit to v12

Author: renovate[bot]

composer.json

@@ -31,7 +31,7 @@
         "guzzlehttp/guzzle": "^6.3|^7.0",
         "mockery/mockery": "^1.3",
         "orchestra/testbench": "^5.0|^6.0|^7.0|^8.0",
-        "phpunit/phpunit": "^9.1|^10.0|^11.0"
+        "phpunit/phpunit": "12.5.6"
     },
     "autoload": {
         "psr-4": {