test: replace anonymous closure function with arrow function

PR-URL: https://github.com/nodejs/node/pull/24435
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ouyang Yadong <oyydoibh@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

test/parallel/test-dgram-send-callback-recursive.js

@@ -29,7 +29,7 @@ client.on('listening', function() {
   onsend();
 });
 
-client.on('message', function(buf, info) {
+client.on('message', (buf, info) => {
   received++;
   if (received === limit) {
     client.close();