build(deps): bump nix from 0.26.4 to 0.28.0

Bumps [nix](https://github.com/nix-rust/nix) from 0.26.4 to 0.28.0.
- [Changelog](https://github.com/nix-rust/nix/blob/master/CHANGELOG.md)
- [Commits](nix-rust/nix@v0.26.4...v0.28.0)

---
updated-dependencies:
- dependency-name: nix
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

pretty_trace/Cargo.toml

@@ -15,7 +15,7 @@ backtrace = "0.3"
 io_utils = { path = "../io_utils", optional = true }
 lazy_static = "1"
 libc = "0.2"
-nix = { version = ">=0.19, <0.28", features = ["signal"] }
+nix = { version = ">=0.19, <0.29", features = ["signal"] }
 stats_utils = { path = "../stats_utils", optional = true }
 string_utils = { path = "../string_utils" }
 tables = { path = "../tables", optional = true }