Get rid of matrix_mautrix_signal_configuration_permissions

While it's kind of nice having it, it's also somewhat raw
and unnecessary.

Having a good default and not even mentioning it seems better
for most users.

People who need a more exposed bridge (rare) can use
override the default configuration using
`matrix_mautrix_signal_configuration_extension_yaml`.

roles/matrix-bridge-mautrix-signal/templates/config.yaml.j2

@@ -172,7 +172,8 @@ bridge:
     #        * - All Matrix users
     #   domain - All users on that homeserver
     #     mxid - Specific user
-    permissions: {{ matrix_mautrix_signal_configuration_permissions }} 
+    permissions:
+      '{{ matrix_mautrix_signal_homeserver_domain }}': user
 
 
 # Python logging configuration.