fix(ci): bump mio fork to complete visionOS cfg gating

Point the mio 0.8.11 patch at setoelkahfi/mio@683fca8, which adds the missing `target_os = "visionos"` entries to the kqueue/net/tcp/uds cfg lists. This fixes the `Check (visionOS device)` and `Check (visionOS simulator)` CI jobs that failed with unresolved `Filter`/`Flags`, `sin_len`/`sin6_len`, `SOCK_NONBLOCK`, and `accept4` errors inside mio. Verified locally: cargo +nightly check -Z build-std --target aarch64-apple-visionos cargo +nightly check -Z build-std --target aarch64-apple-visionos-sim Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>