Update hostname requirement from ^0.3 to ^0.4 (#2206)

Updates the requirements on [hostname](https://github.com/svartalf/hostname) to permit the latest version.
- [Release notes](https://github.com/svartalf/hostname/releases)
- [Changelog](https://github.com/svartalf/hostname/blob/master/CHANGELOG.md)
- [Commits](https://github.com/svartalf/hostname/compare/v0.3.0...v0.4.0)

---
updated-dependencies:
- dependency-name: hostname
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Dominik Maier <domenukk@gmail.com>

libafl_bolts/Cargo.toml

@@ -108,7 +108,7 @@ backtrace = { version = "0.3", optional = true } # Used to get the stacktrace in
 ctor = { optional = true, version = "0.2" }
 serde_json = { version = "1.0", optional = true, default-features = false, features = ["alloc"] }
 miniz_oxide = { version = "0.7.1", optional = true }
-hostname = { version = "^0.3", optional = true } # Is there really no gethostname in the stdlib?
+hostname = { version = "^0.4", optional = true } # Is there really no gethostname in the stdlib?
 rand_core = { version = "0.6", optional = true }
 nix = { version = "0.27", default-features = false, optional = true, features = ["signal", "socket", "poll"] }
 uuid = { version = "1.4", optional = true, features = ["serde", "v4"] }