Revert "test without Access-Control-Allow-Credentials: true (jupyterh…

…ub/mybinder.org-deploy#1344)"

This reverts commit 73238cf.

load_balancer/sites-available/gesis_mybinder

@@ -57,7 +57,7 @@ server {
         # to indicate to browsers that server responses can differ based on the value of the Origin request header
         add_header Vary Origin;
 
-        #add_header "Access-Control-Allow-Credentials"  "true";
+        add_header "Access-Control-Allow-Credentials"  "true";
         add_header 'Access-Control-Allow-Headers' 'cache-control';
         add_header 'Content-Type' 'text/event-stream';
         add_header 'Cache-Control' 'no-cache';