message: Update CHANGELOG for ProtobufRpcClient renaming
diff: @@ -27,6 +27,8 @@ and this project adheres to
  `AuthExtension.unverified.account` return an account of type `Any`. This makes
  the caller responsible for decoding the type.
  - @cosmjs/stargate: Remove `accountFromProto` in favour of `accountFromAny`.
  +- @cosmjs/stargate: Rename `Rpc` interface to `ProtobufRpcClient` and
  + `createRpc` to `createProtobufRpcClient`.
  - @cosmjs/tendermint-rpc: The fields `CommitSignature.validatorAddress`,
  `.timestamp` and `.signature` are now optional. They are unset when
  `blockIdFlag` is `BlockIdFlag.Absent`. The decoding into `CommitSignature` is
  