LWG3002: [networking.ts] `basic_socket_acceptor::is_open()` isn't `noexcept`

[cjdb]

Link: https://wg21.link/lwg3002

libc++ doesn't support the Networking TS, and I'm not aware of any plans for us to do so.

[llvmbot]

@llvm/issue-subscribers-c-20

Author: Christopher Di Bella (cjdb)

**Link:** https://wg21.link/lwg3002

libc++ doesn't support the Networking TS, and I'm not aware of any plans for us to do so.