net::ssl::stream is canonical in examples

We no longer need to use beast::ssl_stream to improve write performance, as
Asio now linearizes scatter/gather I/O in ssl::stream:
https://github.com/chriskohlhoff/asio/commit/17637a48ccbfa2f63941d8393a7c8316a8df4a79

example/http/client/sync-ssl/http_client_sync_ssl.cpp

@@ -17,15 +17,12 @@
 
 #include <boost/beast/core.hpp>
 #include <boost/beast/http.hpp>
-#include <boost/beast/ssl.hpp>
 #include <boost/beast/version.hpp>
 #include <boost/asio/connect.hpp>
 #include <boost/asio/ip/tcp.hpp>
-#include <boost/asio/ssl/error.hpp>
-#include <boost/asio/ssl/stream.hpp>
+#include <boost/asio/ssl.hpp>
 #include <cstdlib>
 #include <iostream>
-#include <string>
 
 namespace beast = boost::beast; // from <boost/beast.hpp>
 namespace http = beast::http;   // from <boost/beast/http.hpp>
@@ -67,7 +64,7 @@ int main(int argc, char** argv)
 
             // These objects perform our I/O
         tcp::resolver resolver(ioc);
-        beast::ssl_stream<beast::tcp_stream> stream(ioc, ctx);
+        ssl::stream<beast::tcp_stream> stream(ioc, ctx);
 
         // Set SNI Hostname (many hosts need this to handshake successfully)
         if(! SSL_set_tlsext_host_name(stream.native_handle(), host))