Update tzdb requirement from 0.5.0 to 0.6.0

Updates the requirements on [tzdb](https://github.com/Kijewski/tzdb) to permit the latest version.
- [Release notes](https://github.com/Kijewski/tzdb/releases)
- [Changelog](https://github.com/Kijewski/tzdb/blob/v0.6.x/CHANGELOG.md)
- [Commits](Kijewski/tzdb@v0.5.0...v0.6.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -28,7 +28,7 @@ time = { version = "0.3.11", features = ["formatting", "local-offset", "parsing"
 git2 = { version = "0.18.0", default-features = false, optional = true }
 
 ## Better support for querying the local system time
-tzdb = { version = "0.5.0", optional = true, default-features = false }
+tzdb = { version = "0.6.0", optional = true, default-features = false }
 
 document-features = { version = "0.2", optional = true }