test: dns utils replace var

PR-URL: #30405
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Carlier <devnexen@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>

lib/internal/dns/utils.js

@@ -52,7 +52,7 @@ class Resolver {
       if (typeof serv !== 'string') {
         throw new ERR_INVALID_ARG_TYPE(`servers[${index}]`, 'string', serv);
       }
-      var ipVersion = isIP(serv);
+      let ipVersion = isIP(serv);
 
       if (ipVersion !== 0)
         return newSet.push([ipVersion, serv, IANA_DNS_PORT]);