Update FAO WIEWS code

@mobreza After speaking to Yassine (BNG) he mentioned that BNG does not have a FAO WIEWS code assigned. I compared the codes for Tunisia in Genesys and in FAO WIEWS and there is a large difference between the two resources (Genesys lists two and FAO WIEWS lists 21). It seems that we need to update the FAO WIEWS list in Genesys.