:bug: pick correct preselected amount on change_currency
:bug: pick correct preselected amount on change_currency

I was passing `state.currency` to pick the featured amount instead of
`action.payload`, which meant the featured amount selected corresponded
to the previous currency's donation band.

This was not caught during testing because all donation bands had the
same amounts (so it always matched an amount).

SumOfUs/Champaign,SumOfUs/Champaign,SumOfUs/Champaign,SumOfUs/Champaign,SumOfUs/Champaign