test: change callback function to arrow function

PR-URL: #17734
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

test/parallel/test-domain-no-error-handler-abort-on-uncaught-9.js

@@ -10,8 +10,8 @@ function test() {
   d.on('error', function errorHandler() {
   });
 
-  d.run(function() {
-    d2.run(function() {
+  d.run(() => {
+    d2.run(() => {
       const fs = require('fs');
       fs.exists('/non/existing/file', function onExists() {
         throw new Error('boom!');