Using REST API to edit submission to closed form

getodk/central-backend#530 made it possible to use the OpenRosa API to edit a submission to a closed form. ~A later PR will make it fully possible to use Enketo to edit a submission to a closed form.~ It is also possible to use the REST API to edit a submission. However, it is not possible right now to use the REST API to edit a submission to a closed form. We should change that so that all edit paths allow a submission to a closed form to be edited.

Making that change will probably look similar to how we updated the OpenRosa API in getodk/central-backend#530: see https://github.com/getodk/central-backend/pull/530#issuecomment-1188554376.