adjust synapse purge jobs template

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

@@ -651,14 +651,7 @@ retention:
   # room's policy to these values is done after the policies are retrieved from
   # Synapse's database (which is done using the range specified in a purge job's
   # configuration).
-  {% if matrix_synapse_retention_purge_jobs | length > 0 %}
-  purge_jobs:
-    {% for job in matrix_synapse_retention_purge_jobs %}
-    - {% if job.longest_max_lifetime is defined %}longest_max_lifetime: {{ job.longest_max_lifetime|to_json }}{% endif %}
-      {% if job.shortest_max_lifetime is defined %}shortest_max_lifetime: {{ job.shortest_max_lifetime|to_json }}{% endif %}
-      {% if job.interval is defined %}interval: {{ job.interval|to_json }}{% endif %}
-    {% endfor %}
-  {% endif %}
+  purge_jobs: {{ matrix_synapse_retention_purge_jobs | to_json }}
   {% endif %}