Update rubocop-minitest requirement from ~> 0.30.0 to ~> 0.31.0

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@v0.30.0...v0.31.0)

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

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

sassc-embedded.gemspec

@@ -31,7 +31,7 @@ Gem::Specification.new do |spec| # rubocop:disable Gemspec/RequireMFA
   spec.add_development_dependency 'minitest-around', '~> 0.5.0'
   spec.add_development_dependency 'rake', '>= 10.0.0'
   spec.add_development_dependency 'rubocop', '~> 1.50.0'
-  spec.add_development_dependency 'rubocop-minitest', '~> 0.30.0'
+  spec.add_development_dependency 'rubocop-minitest', '~> 0.31.0'
   spec.add_development_dependency 'rubocop-performance', '~> 1.17.1'
   spec.add_development_dependency 'rubocop-rake', '~> 0.6.0'
 end