Retire pirogue-admin-wireguard after a while

On the very short term, both `pirogue-admin` and `pirogue-admin-wireguard` are kept as they are, with a little glue to make them usable together, but at least the latter should go away at some point.

For more details, see https://github.com/PiRogueToolSuite/pirogue-admin/commit/ffc9c16b12612a0aeddc3d455d8ac723e25a3a63