build(docs-infra): fix `StackblitzBuilder` after `jsdom` update (#41725)

In commit c617f1f768, `jsdom` was updated
from v9 to v16. This includes a breaking change that caused
`StackblitzBuilder` to fail to generate the StackBlitz examples.
However, this failure went unnoticed, because `StackblitzBuilder` still
completed successfully after failing to generate the examples. (This has
been fixed in the previous commit.)

This commit updates `StackblitzBuilder` to use the new `jsdom` API.

PR Close #41725

aio/tools/stackblitz-builder/builder.js

@@ -254,7 +254,7 @@ class StackblitzBuilder {
 
   _createStackblitzHtml(config, postData) {
     const baseHtml = this._createBaseStackblitzHtml(config);
-    const doc = jsdom.jsdom(baseHtml);
+    const doc = new jsdom.JSDOM(baseHtml).window.document;
     const form = doc.querySelector('form');
 
     for(const [key, value] of Object.entries(postData)) {