Disable healthcheck for Synapse workers which serve no web traffic

This was mostly affecting the stream writer (events) worker, which was
being reported as unhealthy. It wasn't causing any issues, but it just
looked odd and was confusing people.

As an alternative to hitting the regular `/health` healthcheck route (on
the "client" API which this stream writer does not expose),
we may have went for hitting some "replication" API endpoint instead.

This is more complicated and likely unnecessary.

roles/custom/matrix-synapse/tasks/synapse/workers/init.yml

@@ -21,7 +21,7 @@
   ansible.builtin.set_fact:
     worker:
       id: "stream-writer-{{ idx }}-{{ item.stream }}"
-      # Names must not include understores. Certain stream writer streams (to_device, account_data, ..) do, so we fix them up.
+      # Names must not include underscores. Certain stream writer streams (to_device, account_data, ..) do, so we fix them up.
       name: "matrix-synapse-worker-stream-writer-{{ idx }}-{{ item.stream | replace('_', '-') }}"
       type: 'stream_writer'
       app: "generic_worker"

roles/custom/matrix-synapse/templates/synapse/systemd/matrix-synapse-worker.service.j2

@@ -23,7 +23,7 @@ ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} create \
 			--read-only \
 			--tmpfs=/tmp:rw,noexec,nosuid,size={{ matrix_synapse_tmp_directory_size_mb }}m \
 			--network={{ matrix_synapse_container_network }} \
-			{% if matrix_synapse_worker_details.port != 0 %}
+			{% if matrix_synapse_worker_details.port != 0 and matrix_synapse_worker_details.webserving %}
 			--health-cmd 'curl -fSs http://localhost:{{ matrix_synapse_worker_details.port }}/health || exit 1' \
 			{% else %}
 			--no-healthcheck \