test: remove message from notStrictEqual

PR-URL: nodejs/node#16048
Reviewed-By: James Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

test/parallel/test-domain-http-server.js

@@ -51,7 +51,7 @@ const server = http.createServer(function(req, res) {
     const data = JSON.stringify(objects[req.url.replace(/[^a-z]/g, '')]);
 
     // this line will throw if you pick an unknown key
-    assert.notStrictEqual(data, undefined, 'Data should not be undefined');
+    assert.notStrictEqual(data, undefined);
 
     res.writeHead(200);
     res.end(data);