Update minitest requirement from ~> 5.0 to ~> 6.0

Updates the requirements on [minitest](https://github.com/minitest/minitest) to permit the latest version.
- [Changelog](https://github.com/minitest/minitest/blob/master/History.rdoc)
- [Commits](minitest/minitest@v5.0.0...v6.0.0)

---
updated-dependencies:
- dependency-name: minitest
  dependency-version: 6.0.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

Gemfile

@@ -6,7 +6,7 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'appraisal'
-gem 'minitest', '~> 5.0'
+gem 'minitest', '~> 6.0'
 gem 'minitest-reporters', '~> 1.7.1'
 gem 'rake', '~> 13.2'
 gem 'rubocop', '~> 1.73.2'