Do not specify send_federation in Synapse config

It's unnecessary when `federation_sender_instances` is populated.

Source: 6acb6d772a

roles/custom/matrix-synapse/defaults/main.yml

@@ -569,11 +569,6 @@ matrix_synapse_workers_federation_sender_workers_metrics_range_start: 19400
 # Adjusting this value manually is generally not necessary.
 matrix_synapse_federation_sender_instances: []
 
-# matrix_synapse_send_federation controls if the main Synapse process should send federation traffic or if it should be left to federation_sender workers (see `matrix_synapse_federation_sender_instances`).
-# This is allowed if workers are disabled, or they are enabled, but there are no federation sender workers.
-# Adjusting this value manually is generally not necessary.
-matrix_synapse_send_federation: "{{ not matrix_synapse_workers_enabled or (matrix_synapse_workers_enabled_list | selectattr('type', 'equalto', 'federation_sender') | list | length == 0) }}"
-
 matrix_synapse_workers_media_repository_workers_count: "{{ matrix_synapse_workers_presets[matrix_synapse_workers_preset]['media_repository_workers_count'] }}"
 matrix_synapse_workers_media_repository_workers_port_range_start: 18551
 matrix_synapse_workers_media_repository_workers_metrics_range_start: 19551

roles/custom/matrix-synapse/tasks/validate_config.yml

@@ -60,6 +60,8 @@
     - {'old': 'matrix_synapse_workers_frontend_proxy_workers_port_range_start', 'new': '<removed in favor of generic workers - see https://github.com/matrix-org/synapse/pull/13645>'}
     - {'old': 'matrix_synapse_workers_frontend_proxy_workers_metrics_range_start', 'new': '<removed in favor of generic workers - see https://github.com/matrix-org/synapse/pull/13645>'}
     - {'old': 'matrix_synapse_ext_s3_storage_provider_path', 'new': 'matrix_synapse_ext_s3_storage_provider_base_path'}
+    - {'old': 'matrix_synapse_send_federation', 'new': '<unnecessary - Synapse relies on federation_sender_instances now>'}
+
 
 - name: (Deprecation) Catch and report renamed settings in matrix_synapse_configuration_extension_yaml
   ansible.builtin.fail:

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

@@ -2836,12 +2836,6 @@ opentracing:
 
 ## Workers ##
 
-# Disables sending of outbound federation transactions on the main process.
-# Uncomment if using a federation sender worker.
-#
-#send_federation: false
-send_federation: {{ matrix_synapse_send_federation | to_json }}
-
 # It is possible to run multiple federation sender workers, in which case the
 # work is balanced across them.
 #