message: Upgrade UniValue code in zmq/zmqrpc.cpp
  Brings `zmq/zmqrpc.cpp` in line with latest tech.
  Test plan: `ninja bitcoind;test/functional/test_runner.py rpc_zmq`
diff: // Copyright (c) 2018 The Bitcoin Core developers
  +// Copyright (c) 2020 The Bitcoin developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  @@ -31,14 +32,16 @@ UniValue getzmqnotifications(const Config &config,
  HelpExampleRpc("getzmqnotifications", ""));
  }
  - UniValue result(UniValue::VARR);
  + UniValue::Array result;
  if (g_zmq_notification_interface != nullptr) {
  - for (const auto *n :
  - g_zmq_notification_interface->GetActiveNotifiers()) {
  - UniValue obj(UniValue::VOBJ);
  - obj.pushKV("type", n->GetType());
  - obj.pushKV("address", n->GetAddress());
  - result.push_back(obj);
  + auto notifiers = g_zmq_notification_interface->GetActiveNotifiers();
  + result.reserve(notifiers.size());
  + for (const auto *n : notifiers) {
  + UniValue::Object obj;
  + obj.reserve(2);
  + obj.emplace_back("type", n->GetType());
  + obj.emplace_back("address", n->GetAddress());
  + result.emplace_back(std::move(obj));
  }
  }
  