:fire: cautiously enabling PHP 8.4 for unit tests

.github/workflows/ci.yml

@@ -28,10 +28,6 @@ jobs:
           - "8.2"
           - "8.3"
 
-    env:
-      PHAN_ALLOW_XDEBUG: 0
-      PHAN_DISABLE_XDEBUG_WARN: 1
-
     steps:
       - name: "Checkout"
         uses: actions/checkout@v4
@@ -68,6 +64,7 @@ jobs:
         php-version:
           - "8.2"
           - "8.3"
+          - "8.4"
 
     steps:
       - name: "Checkout"