test: fix test case in test-child-process-fork-dgram.js

PR-URL: nodejs#24459
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: gengjiawen

test/parallel/test-child-process-fork-dgram.js

@@ -70,7 +70,7 @@ if (process.argv[2] === 'child') {
     child.on('message', (msg) => {
       if (msg === 'gotMessage') {
         childGotMessage = true;
-      } else if (msg = 'handlReceived') {
+      } else if (msg === 'handleReceived') {
         sendMessages();
       }
     });