Bump jnigen from 0.11.0 to 0.12.0 in /experimental/pedometer

Bumps [jnigen](https://github.com/dart-lang/native/tree/main/pkgs) from 0.11.0 to 0.12.0.
- [Release notes](https://github.com/dart-lang/native/releases)
- [Commits](https://github.com/dart-lang/native/commits/HEAD/pkgs)

---
updated-dependencies:
- dependency-name: jnigen
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

experimental/pedometer/pubspec.yaml

@@ -15,7 +15,7 @@ dependencies:
 
 dev_dependencies:
   ffigen: ^14.0.0
-  jnigen: ^0.11.0
+  jnigen: ^0.12.0
   flutter_test:
     sdk: flutter
   flutter_lints: ^5.0.0