Remove downcasting helper

Author: chipshort

CHANGELOG.md

@@ -17,8 +17,6 @@ and this project adheres to
   `Uint64::from_{be,le}_bytes`. ([#2269])
 - cosmwasm-std: Added new `Ibc2Msg` and `CosmosMsg::Ibc2` variant ([#2340],
   [#2390], [#2403])
-- cosmwasm-std: Implement downcasting for `Api` trait. This allows using
-  `MockApi::addr_make` from `DepsMut`. ([#2457])
 - cosmwasm-std: Added `ibc2_port` to `ContractInfoResponse`. ([#2390], [#2403])
 - cosmwasm-vm: Added `ibc2_packet_receive` entrypoint ([#2403])
 - cosmwasm-vm: Add IBC Callbacks entrypoints to the `Entrypoints` enum.
@@ -99,7 +97,6 @@ and this project adheres to
 [#2432]: https://github.com/CosmWasm/cosmwasm/pull/2432
 [#2433]: https://github.com/CosmWasm/cosmwasm/pull/2433
 [#2438]: https://github.com/CosmWasm/cosmwasm/pull/2438
-[#2457]: https://github.com/CosmWasm/cosmwasm/issues/2457
 
 ## [2.2.0] - 2024-12-17