test: add issue ref for known_issues test

PR-URL: #34267
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: Trott

test/known_issues/test-fs-open-no-close.js

@@ -1,5 +1,6 @@
 'use strict';
 
+// Refs: https://github.com/nodejs/node/issues/34266
 // Failing to close a file should not keep the event loop open.
 
 const common = require('../common');