Update Drupal.org country list to add 'South Sudan'

I added it to the taxonomy list. And updated https://www.drupal.org/case-studies/community → to use the current organization’s location field, so South Sudan can be used as a value. There are a few more places to correct that field, 🐛 Organization page: Remove Offices in field Active

Automatically closed - issue fixed for 2 weeks with no activity.