test: refactor test-http-hostname-typechecking

* Use common.mustCall() to confirm callback is invoked.
* Change spacing of require statements to conform to test-writing guide.

PR-URL: https://github.com/nodejs/node/pull/13993
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-http-hostname-typechecking.js

@@ -1,6 +1,6 @@
 'use strict';
-
 const common = require('../common');
+
 const assert = require('assert');
 const http = require('http');
 
@@ -21,7 +21,7 @@ vals.forEach((v) => {
 // These values are OK and should not throw synchronously
 ['', undefined, null].forEach((v) => {
   assert.doesNotThrow(() => {
-    http.request({hostname: v}).on('error', common.noop).end();
+    http.request({hostname: v}).on('error', common.mustCall()).end();
-    http.request({host: v}).on('error', common.noop).end();
+    http.request({host: v}).on('error', common.mustCall()).end();
   });
 });