Type errors in `currencies` field in JSON export

[Niklas Lindgren]

For these 4 countries the currencies field in the countries.json file is an empty array ([]), which is inconsistent with the rest of the dataset. It should be an empty object ({}) instead.

• Antarctica
• Bouvet Island
• Micronesia
• Heard Island and McDonald Islands

[Mohammed Le Doze]

Hi, this was fixed in #433