message: Add to interface_version_6 changes [skip ci]
diff: @@ -32,6 +32,9 @@ compatibility list:
  - Rename the fields from `send` to `funds` in `WasmMsg::Instantiate` and
  `WasmMsg::Execute`.
  - Merge messages and sub-messages.
  +- Change JSON representation of IBC acknowledgements ([#975]).
  +
  +[#975]: https://github.com/CosmWasm/cosmwasm/pull/975
  ## Setup
  