Hide "Language" column for SPSS exports

[jnm]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure your code lints and you followed our coding style
   @magicznyleszek, this is a 404 for me ☝️ (leads to https://github.com/kobotoolbox/kpi/CONTRIBUTING.md)
5. If this is a big feature, make sure to prefix the title with Feature: and add a thorough description for non-dev folk

Description

Hides "Language" column for existing SPSS exports whose data contains a meaningless lang. Avoids sending lang, group_sep, or hierarchy_in_labels when creating new
SPSS exports.

Related issues

Fixes #2004