Correctly set the credentials of a fetch request, when the withCredentials parameter was passed to getDocument

Skimming through https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API/Using_Fetch#Sending_a_request_with_credentials_included, it looks to me like the `credentials` option was accidentally inverted.

src/display/fetch_stream.js

@@ -26,7 +26,7 @@ function createFetchOptions(headers, withCredentials) {
     method: 'GET',
     headers,
     mode: 'cors',
-    credentials: withCredentials ? 'omit' : 'include',
+    credentials: withCredentials ? 'include' : 'omit',
     redirect: 'follow',
   };
 }