ISO_A2 for France is -99 instead of FR

[JohnRDOrazio]

This issue was fixed upstream in the Natural Earth repo, see:

• issue ISO_A2 for France is -99 instead of FR nvkelso/natural-earth-vector#284
• PR v5 prequel nvkelso/natural-earth-vector#446

Seems that it still needs fixing here though, see for example https://github.com/AshKyd/geojson-regions/blob/main/public/countries/50m/FRA.geojson?short_path=dfa3fad :

"iso_a2":"-99","iso_a2_eh":"FR","iso_a3":"-99","iso_a3_eh":"FRA","iso_n3":"-99","iso_n3_eh":"250"