Turn off IPv6 when using your own Nginx server

Docker apparently doesn't like IPv6.

roles/matrix-synapse/templates/synapse/homeserver.yaml.j2

@@ -144,9 +144,7 @@ listeners:
     # On Linux and Mac OS, `::` will listen on all IPv4 and IPv6
     # addresses by default. For most other OSes, this will only listen
     # on IPv6.
-    bind_addresses:
-      - '::'
-      - '0.0.0.0'
+    bind_addresses: ['::']
 
     # This is a 'http' listener, allows us to specify 'resources'.
     type: http
@@ -174,7 +172,7 @@ listeners:
   # For when matrix traffic passes through loadbalancer that unwraps TLS.
   - port: 8008
     tls: false
-    bind_addresses: ['::', '0.0.0.0']
+    bind_addresses: ['::']
     type: http
 
     x_forwarded: true