message: Fix diff link in CHANGELOG [skip ci]
diff: `FeeTable`. @cosmjs/cosmwasm has its own `FeeTable` with those properties.
  - @cosmjs/sdk38: Rename package to @cosmjs/launchpad.
  -[0.24.0]: https://github.com/CosmWasm/cosmwasm/compare/v0.23.0...v0.24.0
  +[0.24.0]: https://github.com/cosmos/cosmjs/compare/v0.23.0...v0.24.0
  