Fix for pledges list: end -> send

Because the other one was making the browser try to download the
page instead of just opening it. (We actually ran into this before,
but I guess I forgot 😛)

server/index.js

@@ -506,7 +506,7 @@ router.get('/pledges', async (req, res) => {
   twing.render('pledges.htm.twig', {
     'recent_pledges': recentPledges,
   }).then((output) => {
-    res.end(output)
+    res.send(output)
   })
 })