Add conflict for Mockery v1.6.8 (#50468)

Author: driesvints

composer.json

@@ -121,6 +121,7 @@
     "conflict": {
         "carbonphp/carbon-doctrine-types": ">=3.0",
         "doctrine/dbal": ">=4.0",
+        "mockery/mockery": ">=1.6.8",
         "tightenco/collect": "<5.5.33",
         "phpunit/phpunit": ">=11.0.0"
     },