Update deps to SS6 latest

Author: TheSceneman

composer.json

@@ -20,11 +20,11 @@
     ],
     "require": {
         "php": "^8.1",
-        "silverstripe/framework": "^5"
+        "silverstripe/framework": "^6"
     },
     "require-dev": {
-        "phpunit/phpunit": "^9.5",
-        "tractorcow/silverstripe-fluent": "^7",
+        "phpunit/phpunit": "^11",
+        "tractorcow/silverstripe-fluent": "^8",
         "slevomat/coding-standard": "~8.8.0"
     },
     "autoload": {