Deprecate matrix_synapse_spam_checker in favor of matrix_synapse_modules

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

@@ -2570,20 +2570,6 @@ push:
   #group_unread_count_by_room: false
 
 
-# Spam checkers are third-party modules that can block specific actions
-# of local users, such as creating rooms and registering undesirable
-# usernames, as well as remote users by redacting incoming events.
-#
-# spam_checker:
-   #- module: "my_custom_project.SuperSpamChecker"
-   #  config:
-   #    example_option: 'things'
-   #- module: "some_other_project.BadEventStopper"
-   #  config:
-   #    example_stop_events_from: ['@bad:example.com']
-spam_checker: {{ matrix_synapse_spam_checker|to_json }}
-
-
 ## Rooms ##
 
 # Controls whether locally-created rooms should be end-to-end encrypted by