HTTP/3: send Stream Cancellation instruction. As per quic-qpack-21: When a stream is reset or reading is abandoned, the decoder emits a Stream Cancellation instruction. Previously the instruction was not sent. Now it's sent when closing QUIC stream connection if dynamic table capacity is non-zero and eof was not received from client. The latter condition means that a trailers section may still be on its way from client and the stream needs to be cancelled.