Update rubocop-minitest requirement from ~> 0.33.0 to ~> 0.34.1

Updates the requirements on [rubocop-minitest](https://github.com/rubocop/rubocop-minitest) to permit the latest version.
- [Release notes](https://github.com/rubocop/rubocop-minitest/releases)
- [Changelog](https://github.com/rubocop/rubocop-minitest/blob/master/CHANGELOG.md)
- [Commits](rubocop/rubocop-minitest@v0.33.0...v0.34.1)

---
updated-dependencies:
- dependency-name: rubocop-minitest
  dependency-type: direct:development
...

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

gir_ffi-gtk.gemspec

@@ -28,7 +28,7 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rake-manifest", "~> 0.2.0"
   spec.add_development_dependency "rubocop", "~> 1.52"
-  spec.add_development_dependency "rubocop-minitest", "~> 0.33.0"
+  spec.add_development_dependency "rubocop-minitest", "~> 0.34.1"
   spec.add_development_dependency "rubocop-packaging", "~> 0.5.2"
   spec.add_development_dependency "rubocop-performance", "~> 1.18"
   spec.add_development_dependency "rubocop-rake", "~> 0.6.0"