Update Phan to 6.0.0

Author: matsuo

.github/actions/setup-php/action.yaml

@@ -12,7 +12,7 @@ inputs:
   tools:
     description: 'Comma-separated list of tools to install'
     required: false
-    default: composer:2.8.12, phan:6.0.0-beta
+    default: composer:2.8.12, phan:6.0.0
 
 runs:
   using: "composite"