revert: PR 2421 since the Rust issue has been fixed

[SteveLauC]

What does this PR do

Revert #2421 since the Rust issue has been fixed, and the fix should be available in the latest nightly, I guess?

Checklist:

• [x] I have read CONTRIBUTING.md
• [ ] I have written necessary tests and rustdoc comments
• [ ] A change log has been added if this PR modifies nix's API