Add comment on why callback functions are commented in the DAG

dev/dags/example_virtualenv.py

@@ -57,6 +57,9 @@ def example_virtualenv() -> None:
             "install_deps": True,
             "emit_datasets": False,  # Example of how to not set inlets and outlets
             # --------------------------------------------------------------------------
+            # For the sake of avoiding additional latency observed while uploading files for each of the tasks, the
+            # below callback functions to be executed are commented, but you can uncomment them if you'd like to
+            # enable callback execution.
             # Callback function to upload files using Airflow Object storage and Cosmos remote_target_path setting on
             # Airflow 2.8 and above
             # "callback": upload_to_cloud_storage,