Update composer.json

Author: xutongle

composer.json

@@ -13,7 +13,7 @@
     ],
     "require": {
         "php": ">=7.0.0",
-        "laravel/framework": "~5.5",
+        "laravel/framework": "~5.5 | ^6",
         "encore/laravel-admin": "~1.5",
         "predis/predis": "~1.0"
     },