World Subdivisions Layer - outdated ISO 3166-2 codes for CN

[nickpeihl]

It appears the Natural Earth subdivision ISO 3166-2 codes are outdated in China. The ISO 3166-2 codes in China changed from numeric to alpha, e.g. CN-15 -> CN-NM. The GeoIP database also uses the alpha codes so we should update this before releasing.

[jsanz]

I was wondering if we could run a job to compare our existing layers against this global dataset to flag any other potential misaligns. We can fork Natural Earth vector repo to keep changes, even being all in binary files