Make popup a little taller

For some reason the popup was often cutting off the bottom buttons of the UI.

We should look at that more carefully later perhaps, but especially since we're considering moving off the popup, I'm just fixing it by making it taller for now.

app/scripts/lib/notifications.js

@@ -1,5 +1,5 @@
 const extension = require('./extension')
-const height = 500
+const height = 520
 const width = 360
 
 const notifications = {