Init file incorrectly detects duplicated sounds for VOs

Code in question https://github.com/FAForever/fa/blob/deploy/fafdevelop/init_faf.lua#L295-L321

This sounds loading code assumes that sound banks are all directly in the `sounds` folder, but that's not true for voice overs, those always need to be in `sounds/voice/LANGUAGE/bankName.xsb`

So the current code will load the first map with voices and save the `voice` folder incorrectly as a sound bank and won't load any additional VOs in others maps.