message: rpc: Add description to fundrawtransaction vout_index
diff: @@ -3005,7 +3005,7 @@ static UniValue fundrawtransaction(const JSONRPCRequest& request)
  " Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
  " If no outputs are specified here, the sender pays the fee.",
  {
  - {"vout_index", RPCArg::Type::NUM, /* opt */ true, /* default_val */ "", ""},
  + {"vout_index", RPCArg::Type::NUM, /* opt */ true, /* default_val */ "", "The zero-based output index, before a change output is added."},
  },
  },
  {"replaceable", RPCArg::Type::BOOL, /* opt */ true, /* default_val */ "", "Marks this transaction as BIP125 replaceable.\n"
  