fix arg url always be libredns
If --dns choose another dns, the request will always send to libredns
doh-cli --verbose --dns cloudflare www.google.com
142.250.184.228
Verbose:
https://doh.libredns.gr/dns-query?dns=9K0BAAABAAAAAAAAA3d3dwZnb29nbGUDY29tAAABAAE
after the fix,
doh-cli --verbose --dns cloudflare www.google.com
172.217.17.132
Verbose:
https://cloudflare-dns.com/dns-query?dns=EioBAAABAAAAAAAAA3d3dwZnb29nbGUDY29tAAABAAE