I don't think this URL actually matters anymore, but I believe it's required to be present by Salesforce. When you plop in a default Salesforce form, it POSTs directly to Salesforce, then sends the user on to the URL specified by `retURL`. Thanks to our fancy proxy here, the user is never POSTing directly to Salesforce (regardless of originating URL, with or without JS), so `retURL` is never visited/seen.

We probably want to keep it pointing to a valid URL just in case, but I don't think it needs any logic around it.