Hi @brain_in_a_box,
Here is the updated link to the raw notebook https://github.com/nengo/nengo/blob/master/docs/examples/advanced/inhibitory-gating.ipynb .
All of the examples are also available in an easier to read form here https://www.nengo.ai/nengo/examples, including that one https://www.nengo.ai/nengo/examples/advanced/inhibitory-gating.html.