[libcxx-commits] [libcxx] [libc++] Mark LWG3403 as resolved (PR #208866)

[A. Jiang via libcxx-commits]

https://github.com/frederick-vs-ja approved this pull request.

Thanks! I shortened PR description to avoid pasting the concrete test code, as someone who want to know the detail of the test coverage should read the original commit, IMO. Feel free to modify the PR description again.

https://github.com/llvm/llvm-project/pull/208866