http2: skip creating native ShutdownWrap

`ShutdownWrap` instances are being used to carry context between the
start and the asynchronous end of shutting down the writable side of
a `StreamBase`. HTTP/2 streams always perform this action
synchronously, so no such object is necessary.

PR-URL: https://github.com/nodejs/node/pull/31283


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>