Update unreachable requirement from 0.1 to 1.0

Updates the requirements on [unreachable](https://github.com/reem/rust-unreachable) to permit the latest version.
- [Release notes](https://github.com/reem/rust-unreachable/releases)
- [Commits](https://github.com/reem/rust-unreachable/commits/1.0.0)

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

rustler_sys/Cargo.toml

@@ -35,4 +35,4 @@ build = "build.rs"
 categories = ["external-ffi-bindings"]
 
 [dependencies]
-unreachable = "0.1"
+unreachable = "1.0"