test: fix parallel/test-dgram-udp6-link-local-address

Refs: nodejs#41431

PR-URL: nodejs#42795
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-dgram-udp6-link-local-address.js

@@ -12,7 +12,7 @@ const { isWindows } = common;
 function linklocal() {
   for (const [ifname, entries] of Object.entries(os.networkInterfaces())) {
     for (const { address, family, scopeid } of entries) {
-      if (family === 'IPv6' && address.startsWith('fe80:')) {
+      if (family === 6 && address.startsWith('fe80:')) {
         return { address, ifname, scopeid };
       }
     }