ListDataFile is not documented as a paginated list in OpenAPI

As noted in #1186, the ListDataFile endpoint is documented strangely, with Spectacular not understanding that it is a list endpoint and calling it RetrieveDataFile2 by default. A hack is in place to cause the endpoint to still be called ListDataFile, but this does not make it appear as a list, or documents pagination. This causes the API client to be unable to paginate it, since the backend reports x-paginated: false.