changed key name to reflect relative path

ark_example.py

@@ -59,8 +59,8 @@ _URL_DATASET_CONFIGS = {
     "nb1": {"image_data": _URL_DATA["image_data"]},
     "nb2": {
         "image_data": _URL_DATA["image_data"],
-        "cell_table": _URL_DATA["cell_table"],
-        "deepcell_output": _URL_DATA["deepcell_output"],
+        "segmentation/cell_table": _URL_DATA["cell_table"],
+        "segmentation/deepcell_output": _URL_DATA["deepcell_output"],
     },
 }