Add oo-hetzner-03 as second backend to other backendless Onionoo hosts
As of now, oo-hetzner-03 is both backend and its own frontend, and omeiense is backend to a couple other frontends (and itself). Unless there are any issues with oo-hetzner-03, we should add it as second backend to the other backendless hosts. But let's give it a few days first to see how it behaves. (Thanks!)