Update rb-sys-test-helpers requirement in /ext/ruby_native_statistics (#88)

Updates the requirements on [rb-sys-test-helpers](https://github.com/oxidize-rb/rb-sys) to permit the latest version.
- [Release notes](https://github.com/oxidize-rb/rb-sys/releases)
- [Commits](https://github.com/oxidize-rb/rb-sys/commits/v0.3.0)

---
updated-dependencies:
- dependency-name: rb-sys-test-helpers
  dependency-version: 0.3.0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

ext/ruby_native_statistics/Cargo.toml

@@ -11,7 +11,7 @@ rb-sys-env = "0.2"
 
 [dev-dependencies]
 rb-sys-env = { version = "0.2" }
-rb-sys-test-helpers = { version = "0.2" }
+rb-sys-test-helpers = { version = "0.3" }
 
 [dependencies]
 magnus = { version = "0.8.0" }