remove unnecessary serialisation when exporting countries in JS (bug 1099285)

https://bugzilla.mozilla.org/show_bug.cgi?id=1099285

r? @mstriemer @ngokevin 

instead of making it a string and thne `JSON.parse`-ing it, I just return the object itself. assuming nobody sneaks in some exploitable code in this repo, we should be fine. if people agree that it's not worth the risk of people sneaking in functions here, let me know and I don't have to do this.