Incorrect `getSupplyAt`

[onmax]

https://github.com/nimiq/core-rs-albatross/blob/d555468a9eba6f43264daaad30037d74c4ce7afe/rpc-interface/src/policy.rs#L94

async fn get_supply_at(
    &self,
    genesis_supply: u64,
    genesis_time: u64,
    current_time: u64,
) -> RPCResult<u64, (), Self::Error>;