Cannot use ipv6 address as URL

Ping works:
```
$ ping fe80::5017:d7ff:feb8:a43e%ve-local-arwyas
PING fe80::5017:d7ff:feb8:a43e%ve-local-arwyas(fe80::5017:d7ff:feb8:a43e%ve-local-arwyas) 56 data bytes
64 bytes from fe80::5017:d7ff:feb8:a43e%ve-local-arwyas: icmp_seq=1 ttl=64 time=0.050 ms
64 bytes from fe80::5017:d7ff:feb8:a43e%ve-local-arwyas: icmp_seq=2 ttl=64 time=0.037 ms
64 bytes from fe80::5017:d7ff:feb8:a43e%ve-local-arwyas: icmp_seq=3 ttl=64 time=0.044 ms
^C
--- fe80::5017:d7ff:feb8:a43e%ve-local-arwyas ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2043ms
rtt min/avg/max/mdev = 0.037/0.043/0.050/0.005 ms
```
But oha does not:
```
$ oha --ipv6 https://fe80::5017:d7ff:feb8:a43e%ve-local-arwyas
error: Invalid value "https://fe80::5017:d7ff:feb8:a43e%ve-local-arwyas" for '': invalid authority

For more information try --help
```

It's an address of a systemd-nspawn container.

```
$ oha --version
oha 0.5.3
```