`wg show` command shows entire interfaces configuration, not just the
list. This breaks completion when running fish from root, because
command output looks like this:
interface: wg0
public key: fred2rX85AxpcTObLuiWTzkRPZaXjnhd1C4XOdZOGWs=
private key: (hidden)
listening port: 12345
fwmark: 0xca6c
peer: g2YHHDkxmgoT9EV0TxKtq556WLXpaOh4zgC5L7EAGTQ=
endpoint: 192.168.88.50:54321
allowed ips: 0.0.0.0/0, ::/0
latest handshake: 1 minute, 37 seconds ago
transfer: 1.83 MiB received, 927.19 KiB sent
To show just the list of active interfaces, `wg show interfaces` should
be used instead.
