chore(deps): update sysctl requirement from 0.2 to 0.3

Updates the requirements on [sysctl](https://github.com/johalun/sysctl-rs) to permit the latest version.
- [Release notes](https://github.com/johalun/sysctl-rs/releases)
- [Changelog](https://github.com/johalun/sysctl-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/johalun/sysctl-rs/commits)

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

Cargo.toml

@@ -20,4 +20,4 @@ failure = "0.1"
 libc = "0.2"
 nix = "0.13"
 number_prefix = "0.2"
-sysctl = "0.2"
+sysctl = "0.3"