Bump the rbs-dependencies group with 1 update

Updates the requirements on [rbs](https://github.com/ruby/rbs) to permit the latest version.

Updates `rbs` to 3.4.0
- [Release notes](https://github.com/ruby/rbs/releases)
- [Changelog](https://github.com/ruby/rbs/blob/master/CHANGELOG.md)
- [Commits](ruby/rbs@v3.3.2...v3.4.0)

---
updated-dependencies:
- dependency-name: rbs
  dependency-type: direct:development
  dependency-group: rbs-dependencies
...

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

Gemfile

@@ -12,7 +12,7 @@ end
 
 group(:development) do
   gem('debug', '~> 1.9.0', require: false)
-  gem('rbs', '~> 3.3.2', require: false)
+  gem('rbs', '~> 3.4.0', require: false)
   gem('steep', '~> 1.6.0', require: false)
   gem('benchmark-ips', '~> 2.13.0', require: false)
   gem('stackprof')