Remove unnecessary function

on_stream_close is called after on_frame_not_send_callback with
success=false without this function.

src/h2load_http2_session.cc

@@ -105,23 +105,6 @@ int on_stream_close_callback(nghttp2_session *session, int32_t stream_id,
 }
 } // namespace
 
-namespace {
-int on_frame_not_send_callback(nghttp2_session *session,
-                               const nghttp2_frame *frame, int lib_error_code,
-                               void *user_data) {
-  if (frame->hd.type != NGHTTP2_HEADERS ||
-      frame->headers.cat != NGHTTP2_HCAT_REQUEST) {
-    return 0;
-  }
-
-  auto client = static_cast<Client *>(user_data);
-  // request was not sent.  Mark it as error.
-  client->on_stream_close(frame->hd.stream_id, false);
-
-  return 0;
-}
-} // namespace
-
 namespace {
 int before_frame_send_callback(nghttp2_session *session,
                                const nghttp2_frame *frame, void *user_data) {
@@ -211,9 +194,6 @@ void Http2Session::on_connect() {
   nghttp2_session_callbacks_set_on_header_callback(callbacks,
                                                    on_header_callback);
 
-  nghttp2_session_callbacks_set_on_frame_not_send_callback(
-      callbacks, on_frame_not_send_callback);
-
   nghttp2_session_callbacks_set_before_frame_send_callback(
       callbacks, before_frame_send_callback);