I think the problem is that widgets are not supported in Google Colab.
As you are storing the images in Google Drive you could just go in there and delete some. However the widget is worth a go so I would recommend setting up a local Jupyter environment, connect to your Google Drive and then run the widget. Once you have run the widget a csv is generated. I would recommend then going back to Google Colab to complete the lesson (as it is likely to be faster than your local environment).