fix(maitake-sync): don't enable portable-atomic/critical-section

## Summary - The `critical-section` feature in both `maitake-sync` and `maitake` was enabling `portable-atomic/critical-section`, which conflicts with `portable-atomic/unsafe-assume-single-core` (used by e.g. esp-hal for ESP32-C3) - Per [portable-atomic's docs](https://docs.rs/portable-atomic/latest/portable_atomic/#optional-cfg), libraries should leave the portable-atomic backend choice to the end user - Updated the no-atomics CI check to explicitly pass `portable-atomic/critical-section`, simulating what an end user on a no-CAS target would do Fixes #559