add that the feature is experimental

taxonomy/classifications.json

@@ -447,6 +447,6 @@
     "group:*": {
         "name": "group:*",
         "label": "Attacker Group: *",
-        "description": "This IP is part of a group of machines that exploit the same set of vulnerabilities in a synchronized manner, indicating potential control by a common threat actor."
+        "description": "This IP is part of a group of machines that exploit the same set of vulnerabilities in a synchronized manner, indicating potential control by a common threat actor.This is currently an experimental feature."
     }
 }