remove redundant flush() from example:

`<<std::endl` already flushes the stream; no need for a separate call.

CHANGELOG.md

@@ -6,6 +6,7 @@ Version 74:
 * Remove common/file_body.hpp
 * Add file_posix
 * Fix Beast include directories for cmake targets
+* remove redundant flush() from example
 
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example/http-client/http_client.cpp

@@ -25,7 +25,6 @@ int main()
         [](std::string what, beast::error_code ec)
         {
             std::cerr << what << ": " << ec.message() << std::endl;
-            std::cerr.flush();
             return EXIT_FAILURE;
         };