types/dnstype: use viewer instead of cloner
This was missed when I did the initial viewer work.
// Package dnstype defines types for working with DNS.
package dnstype
-//go:generate go run tailscale.com/cmd/cloner --type=Resolver --clonefunc=true
+//go:generate go run tailscale.com/cmd/viewer --type=Resolver --clonefunc=true
import (
"net/netip"
