message: review fix (hopefully)
diff: @@ -53,18 +53,12 @@ Response Schema
  }
  message EngineReceipt {
  int32 command_index = 1;
  - string tx_hash = 2; // hex string
  - int32 tx_index = 3;
  - string block_hash = 4; // hex string
  - uint64 block_height = 5;
  - string from = 6; // sender account id
  - oneof opt_to {
  - string to = 7; // hex receiver EVM address
  - }
  - oneof opt_contract_address {
  - string contract_address = 8; // hex string
  - }
  - repeated EngineLog logs = 9;
  + string caller = 2;
  + oneof opt_to_contract_address {
  + CallResult call_result = 3;
  + string contract_address = 4;
  + }
  + repeated EngineLog logs = 5;
  }
  message EngineLog {
  string address = 1; // hex string
  