fix silver and souls index in UnderworldResourceType struct

[tjira]

The indices of silver and souls were swapped. This commit fixes the bug so that UnderworldCollect collects the correct resources.

[the-marenga]

Thanks! I think the reason why I had this enum order is because that is the order the resources are parsed in and for most things, that is then also their variant ordering. In this case though, you are right, they are swapped. In theory, doing this swap behind the scenes (in request_string()) could be a less of a breasking change, if anyone downstream relied on the numeric value, but the main branch already contains a bunch of breaking changes, that it should be fine.

Thanks again and good luck with your rsfb bot!