To answer my own question, if you Google "what is cdn.optimizely.com" you will see what a content delivery network does. From my reading it looks like it caches web pages to improve Quickbooks performance and allows for A/B testing of web pages. If your use of Quickbooks doesn't need web pages, my guess is it is safe to block this URL. Maybe Quickbooks mistakenly, or purposefully, discontinued the use of this Optimizely CDN.
