Use latest version of Redoc for previews. (#983)

Author: andrewsomething

docs-preview/redoc-index.html

@@ -103,7 +103,7 @@
         document.querySelector('redoc').setAttribute('spec-url', specUrl);
     </script>
 
-    <script src="https://cdn.jsdelivr.net/npm/redoc@2.0.0-rc.50/bundles/redoc.standalone.js"> </script>
+    <script src="https://cdn.redoc.ly/redoc/latest/bundles/redoc.standalone.js"> </script>
 </body>
 
 </html>