[Data update] remove Kosovo from the list of countries; not in ISO 3166

[o-alexandrov]

Data changes

Kosovo should be removed from the list of countries.
Or the main readme.md file should be updated to mention the data is not conforming to ISO 3166

Links & sources

• ISO 3166 list of countries
• Related PR in a similar library

[dmythro]

User-assigned codes is a part of a standard. But I think it would be clearer for them to actually have a temporary or userAssigned flag set in order to properly differentiate.

User-assigned code elements are codes at the disposal of users who need to add further names of countries, territories, or other geographical entities to their in-house application of ISO 3166-1, and the ISO 3166/MA will never use these codes in the updating process of the standard. The following alpha-2 codes can be user-assigned: AA, QM to QZ, XA to XZ, and ZZ.

The code XK is being used by the European Commission the IMF, and SWIFT, the CLDR, and other organizations as a temporary country code for Kosovo.

See: https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2#User-assigned_code_elements