Use name-resolution for 1.1.1.1 service

The service has 4 IP-addresses, and I was the fortunate guy to run into an issue with an ISP breaking 1.1.1.1 (but not 1.0.0.1). This also fixes IPv6-only networks.
```
$ host one.one.one.one
one.one.one.one has address 1.0.0.1
one.one.one.one has address 1.1.1.1
one.one.one.one has IPv6 address 2606:4700:4700::1111
one.one.one.one has IPv6 address 2606:4700:4700::1001
```

acme.sh

@@ -3620,7 +3620,7 @@ _ns_purge_cf() {
   if [ "$CLOUDFLARE_DOHJSON_URL" != "" ]; then
     _cf_purl="$ONE_ONE_ONE_ONE_URL?domain=$_cf_d&type=$_cf_d_type"
   else
-    _cf_purl="https://1.1.1.1/api/v1/purge?domain=$_cf_d&type=$_cf_d_type"
+    _cf_purl="https://one.one.one.one/api/v1/purge?domain=$_cf_d&type=$_cf_d_type"
   fi
   response="$(_post "" "$_cf_purl")"
   _debug2 response "$response"