[libc++] Update some C++23 statuses to "Nothing to do" or "Complete" (#99621)

- [P2160R1][] "Locks lock lockables"
- [P2212R2][] "Relax Requirements for `time_point::clock`"
- [P1675R2][] "`rethrow_exception` must be allowed to copy"
- [P2340R1][] "Clarifying the status of the 'C headers'"
- [P2460R2][] "Relax requirements on `wchar_t` to match existing

Are all papers that change wording without changing implementation

Additionally, [P2736R2][] "Referencing The Unicode Standard", is an
already complete paper in 19.0 (as of [LLVM-86543][])

[P2160R1]: https://wg21.link/p2160r1
[P2212R2]: https://wg21.link/p2212r2
[P1675R2]: https://wg21.link/p1675r2
[P2340R1]: https://wg21.link/p2340r1
[P2460R2]: https://wg21.link/p2460r2
[P2736R2]: https://wg21.link/p2736r2
[LLVM-86543]: https://github.com/llvm/llvm-project/pull/86543

GitOrigin-RevId: 418922623673a8044d30a57825b026a03f9d9354
1 file changed