example/cppcon2018 is removed:

* Replaced by websocket-chat-multi

doc/qbk/02_examples/0_examples.qbk

@@ -215,9 +215,9 @@ and illustrate the implementation of advanced features.
 This talk was given at [@https://cppcon.org CppCon 2018]. In this
 presentation, we develop a multi-user chat server written in C++ using
 Beast WebSocket, which uses a provided chat client written in HTML and
-JavaScript. The source files for this example are located at
-[source_file example/cppcon2018].
-
+JavaScript. An improved, multi-threaded version of this program is
+included here
+[source_file example/websocket/server/chat-multi].
 
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