Bump nix from 0.15.0 to 0.16.0 (#7216)

Bumps [nix](https://github.com/nix-rust/nix) from 0.15.0 to 0.16.0.
- [Release notes](https://github.com/nix-rust/nix/releases)
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](https://github.com/nix-rust/nix/commits/v0.16.0)

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

core/Cargo.toml

@@ -33,7 +33,7 @@ lazy_static = "1.4.0"
 libc = "0.2.66"
 log = "0.4.8"
 memmap = { version = "0.7.0", optional = true }
-nix = "0.15.0"
+nix = "0.16.0"
 num-traits = "0.2"
 rand = "0.6.5"
 rand_chacha = "0.1.1"