Fix exception on start up about device lists (#15041)

Fixes #15010.

changelog.d/15041.misc

@@ -0,0 +1 @@
+Fix a rare exception in logs on start up.

synapse/storage/databases/main/devices.py

@@ -100,6 +100,7 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore):
                 ("device_lists_outbound_pokes", "stream_id"),
                 ("device_lists_changes_in_room", "stream_id"),
                 ("device_lists_remote_pending", "stream_id"),
+                ("device_lists_changes_converted_stream_position", "stream_id"),
             ],
             is_writer=hs.config.worker.worker_app is None,
         )