live2dev: drop yarn stuff from update script

Following updates in https://github.com/cotech/website/pull/90/files.

Looks like we might need to think about not doing:

https://git.coop/cotech/ansible/blob/master/roles/live2dev/templates/update.j2#L27

I'm still getting to grips with the and I think the current development setup is borked (so let's not deploy).

But think we need to update this script in some fashion ...