Update meta.json

classes/class04/meta.json

@@ -2,6 +2,6 @@
     "name": "Class 04 - Detect Intruders",
     "id": "class-04",
     "description": "The fourth class focuses on detecting intruders in your server. Please open the Google document provided to all registered students and follow the document.",
-    "google_doc_url": "",
+    "google_doc_url": "https://docs.google.com/document/d/1olPwIt3AWtyfj4uFJAIsQxkTFyWnxNtHCXhA0uMc1PI",
     "yt_recording_url": ""
 }