Update env_logger requirement from 0.7.1 to 0.8.1

Updates the requirements on [env_logger](https://github.com/env-logger-rs/env_logger) to permit the latest version.
- [Release notes](https://github.com/env-logger-rs/env_logger/releases)
- [Changelog](https://github.com/env-logger-rs/env_logger/blob/master/CHANGELOG.md)
- [Commits](https://github.com/env-logger-rs/env_logger/compare/v0.7.1...v0.8.1)

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

Cargo.toml

@@ -20,7 +20,7 @@ coarsetime = "0.1.16"
 daemonize-simple = "0.1.4"
 derivative = "2.1.1"
 dnsstamps = "0.1.4"
-env_logger = { version = "0.7.1", default-features = false, features = ["humantime"] }
+env_logger = { version = "0.8.1", default-features = false, features = ["humantime"] }
 futures = { version = "0.3.5", features = ["async-await"] }
 hyper = { version = "0.13.8", default_features = false, optional = true }
 ipext = "0.1.0"