message: [rpc] reserve space in txns
diff: @@ -924,6 +924,7 @@ static RPCHelpMan testmempoolaccept()
  }
  std::vector<CTransactionRef> txns;
  + txns.reserve(raw_transactions.size());
  for (const auto& rawtx : raw_transactions.getValues()) {
  CMutableTransaction mtx;
  if (!DecodeHexTx(mtx, rawtx.get_str())) {
  