在为 HTTP/2 流设置优先级时，该流可能会被标记为父流的依赖。当尝试将流标记为自身的依赖时，会使用此错误代码。
【When setting the priority for an HTTP/2 stream, the stream may be marked as
a dependency for a parent stream. This error code is used when an attempt is
made to mark a stream and dependent of itself.】