Katacoda: configure the minikube to use a local domain name

@sbawaska commented on [Tue Mar 30 2021](https://github.com/knative/docs/issues/3402)

**Describe the change you'd like to see**
In the katacoda tutorials being discussed in #3142, rather than using the minikube IP, it would better to use a local domain name such as `http://demo.default.127.0.0.1.nip.io`. see comment here: https://github.com/knative/docs/pull/3142#discussion_r598965848

Review the Katacoda tutorials discussed in #3142 and the linked discussion on pull request #3142. Find where the tutorials use the Minikube IP and update that usage to the proposed local domain pattern. Done means the tutorials use the local domain name instead of the Minikube IP.

Written by the indexing model from the issue text.