build(deps-dev): bump rbs from 3.8.1 to 3.9.0

Bumps [rbs](https://github.com/ruby/rbs) from 3.8.1 to 3.9.0.
- [Release notes](https://github.com/ruby/rbs/releases)
- [Changelog](https://github.com/ruby/rbs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ruby/rbs/compare/v3.8.1...v3.9.0)

---
updated-dependencies:
- dependency-name: rbs
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Gemfile.lock

@@ -114,7 +114,7 @@ GEM
     rb-fsevent (0.11.2)
     rb-inotify (0.11.1)
       ffi (~> 1.0)
-    rbs (3.8.1)
+    rbs (3.9.0)
       logger
     regexp_parser (2.10.0)
     rexml (3.4.1)