only allow Backpack v6

Author: tabacitu

composer.json

@@ -12,8 +12,8 @@
     "homepage": "https://github.com/laravel-backpack/filemanager",
     "keywords": ["Laravel", "FileManager"],
     "require": {
-        "backpack/crud": "^5.0|^6.0|6.x-dev",
-        "barryvdh/laravel-elfinder": "^0.5.0"
+        "backpack/crud": "^6.0",
+        "barryvdh/laravel-elfinder": "^0.5.2"
     },
     "require-dev": {
         "phpunit/phpunit": "^10.0",