rpc: remove deprecated resolver::query

`boost::asio::ip::tcp::resolver::query` has been removed in 1.87 which
causes compilation issues.

This raises the minimum supported version of Boost to 1.66 which should
be safe since near-EOL focal has 1.71.

Author: div72

src/rpc/protocol.h

@@ -143,8 +143,7 @@ class SSLIOStreamDevice : public boost::iostreams::device<boost::iostreams::bidi
     bool connect(const std::string& server, const std::string& port)
     {
         boost::asio::ip::tcp::resolver resolver(GetIOService(stream));
-        boost::asio::ip::tcp::resolver::query query(server.c_str(), port.c_str());
-        boost::asio::ip::tcp::resolver::iterator endpoint_iterator = resolver.resolve(query);
+        boost::asio::ip::tcp::resolver::iterator endpoint_iterator = resolver.resolve(server, port);
         boost::asio::ip::tcp::resolver::iterator end;
         boost::system::error_code error = boost::asio::error::host_not_found;
         while (error && endpoint_iterator != end)