test: replaced functions with arrow functions

PR-URL: #23511
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/parallel/test-domain-from-timer.js

@@ -27,11 +27,11 @@ const assert = require('assert');
 
 // timeouts call the callback directly from cc, so need to make sure the
 // domain will be used regardless
-setTimeout(function() {
+setTimeout(() => {
   const domain = require('domain');
   const d = domain.create();
-  d.run(function() {
-    process.nextTick(function() {
+  d.run(() => {
+    process.nextTick(() => {
       console.trace('in nexttick', process.domain === d);
       assert.strictEqual(process.domain, d);
     });