Bump fern from 0.5.9 to 0.6.0

Bumps [fern](https://github.com/daboross/fern) from 0.5.9 to 0.6.0.
- [Release notes](https://github.com/daboross/fern/releases)
- [Changelog](https://github.com/daboross/fern/blob/master/CHANGELOG.md)
- [Commits](https://github.com/daboross/fern/compare/fern-0.5.9...fern-0.6.0)

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

Cargo.toml

@@ -20,7 +20,7 @@ reqwest = "0.9"
 crossbeam-channel = "0.5"
 platform-dirs = "0.3.0"
 failure = "0.1"
-fern = "0.5"
+fern = "0.6"
 futures = { version = "0.3", features = ["compat"] }
 futures_01 = { version = "0.1", package = "futures" }
 lazy_static = "1.3.0"