test: fix reference to WPT testharness.js

The W3C testharness.js was moved to the `web-platform-tests/wpt`
repository a while ago.

PR-URL: #35814
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/common/wpt.js

@@ -9,7 +9,7 @@ const path = require('path');
 const { inspect } = require('util');
 const { Worker } = require('worker_threads');
 
-// https://github.com/w3c/testharness.js/blob/master/testharness.js
+// https://github.com/web-platform-tests/wpt/blob/master/resources/testharness.js
 // TODO: get rid of this half-baked harness in favor of the one
 // pulled from WPT
 const harnessMock = {