docs: Update sponsors

docs/sponsors.rst

@@ -11,23 +11,25 @@ the project.
 Rackspace
 =========
 
-`Rackspace <http://www.rackspace.com/>`_ lets Mopidy use their hosting services
-for free. We use their services for the following sites:
+`Rackspace <https://www.rackspace.com/>`_ lets Mopidy use their hosting
+services for free. We use their services for the following sites:
 
 - Hosting of the APT package repository at https://apt.mopidy.com.
 
-- Hosting of the Discourse forum at https://discourse.mopidy.com.
-
-- Mailgun for sending emails from the Discourse forum.
+- OAuth bridges at https://auth.mopidy.com.
 
 
 Fastly
 ======
 
 `Fastly <https://www.fastly.com/>`_ lets Mopidy use their CDN for free. We
-accelerate requests to all Mopidy services, including:
+accelerate requests to most Mopidy services, including:
 
 - https://apt.mopidy.com/dists/, which is used to distribute Debian packages.
 
-- https://dl.mopidy.com/pimusicbox/, which is used to distribute Pi Musicbox
-  images.
+
+Discourse
+=========
+
+`Discourse <https://www.discourse.org/>`_ sponsors Mopidy with free hosting of
+our discussion forum at https://discourse.mopidy.com.