Update nix requirement from 0.30.1 to 0.31.2

Updates the requirements on [nix](https://github.com/nix-rust/nix) to permit the latest version.
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](nix-rust/nix@v0.30.1...v0.31.2)

---
updated-dependencies:
- dependency-name: nix
  dependency-version: 0.31.2
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Cargo.toml

@@ -135,7 +135,7 @@ libvharness_sys = { path = "./crates/libafl_qemu/libvharness_sys", version = "0.
 log = "0.4.29"
 meminterval = "0.4.2"
 mimalloc = { version = "0.1.48", default-features = false }
-nix = { version = "0.30.1", default-features = false }
+nix = { version = "0.31.2", default-features = false }
 num_enum = { version = "0.7.4", default-features = false }
 num-traits = { version = "0.2.19", default-features = false }
 paste = "1.0.15"