dns: cleanup validation

The `validateString()` validator should cleanup the validation and
keep consistency.

PR-URL: #40061
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/internal/dns/utils.js

@@ -32,7 +32,6 @@ const IPv6RE = /^\[([^[\]]*)\]/;
 const addrSplitRE = /(^.+?)(?::(\d+))?$/;
 const {
   ERR_DNS_SET_SERVERS_FAILED,
-  ERR_INVALID_ARG_TYPE,
   ERR_INVALID_ARG_VALUE,
   ERR_INVALID_IP_ADDRESS,
 } = errors.codes;
@@ -131,8 +130,8 @@ class Resolver {
   setLocalAddress(ipv4, ipv6) {
     validateString(ipv4, 'ipv4');
 
-    if (typeof ipv6 !== 'string' && ipv6 !== undefined) {
-      throw new ERR_INVALID_ARG_TYPE('ipv6', ['String', 'undefined'], ipv6);
+    if (ipv6 !== undefined) {
+      validateString(ipv6, 'ipv6');
     }
 
     this._handle.setLocalAddress(ipv4, ipv6);