http2: do no throw in writeHead if state.closed

The http1 implementation does not throw if the connection is down.
The http2 compat implementation should do the same.

See: https://github.com/fastify/fastify-http-proxy/issues/51.
See: https://github.com/fastify/fastify/issues/1494.

PR-URL: https://github.com/nodejs/node/pull/27682


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