Remove livestream test helpers
Remove livestream test helpers

These test helpers are no longer being used.

The current live stream of press conferences used to be streamed on the
coronavirus landing page. However this stopped in summer 2020 and hasn't
been used since). The code is being removed as it's no being used and
its presence makes it harder to add features in collections-publisher.

alphagov/collections-publisher,alphagov/collections-publisher,alphagov/collections-publisher