Update kapp-controller asciinema video to show more realistic PackageRepository

Currently, the kapp-controller webpage features a small demo video shown [here](https://carvel.dev/kapp-controller/#examples). The PackageRepository shown in the video features sample Packages (i.e. `simple-app.corp.com`).

However, changing this to showcase a repository with more meaningful Packages (e.g. [cert-manager](https://cert-manager.io/docs/)) would help users better understand kapp-controller. Using the simple-app Package isn't the perfect illustration of kapp-controller's capabilities.

The [asciinema video](https://github.com/vmware-tanzu/carvel/tree/develop/asciinema) is maintained here in the carvel repo. There should also be some discussion about what PackageRepository to use in the video.

Start in the asciinema directory and inspect the video used on the kapp-controller webpage at the examples section. Review the current PackageRepository and its sample Packages, then determine which more meaningful repository to showcase, such as cert-manager. Done means the video and its webpage presentation use the agreed realistic PackageRepository.

Written by the indexing model from the issue text.