Replace `unwrap_or_else(|e| e.into_inner())` with `expect("env mutex poisoned")`
in bind_rejects_wildcard_ipv4 and bind_rejects_wildcard_ipv6 tests to match the
ENV_MUTEX pattern used in oauth_defaults.rs. The old pattern silently recovered
from a poisoned mutex, potentially allowing concurrent env var access when a
prior test panicked while holding the lock.
[skip-regression-check]
Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>