[webhooks server] rely on SPACE_ID to check if app is local or in a Sapce (#2450)

Author: Wauplin

src/huggingface_hub/_webhooks_server.py

@@ -36,7 +36,7 @@
 
 
 _global_app: Optional["WebhooksServer"] = None
-_is_local = os.getenv("SYSTEM") != "spaces"
+_is_local = os.environ.get("SPACE_ID") is None
 
 
 @experimental