chore(deps): update dependency minitest to v6 (#151)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Gemfile

@@ -8,7 +8,7 @@ group :test do
   gem "kitchen-dokken"
   gem "kitchen-vagrant"
   gem "rake"
-  gem "minitest", "~> 5.3", "< 6.0"
+  gem "minitest", "~> 6.0", "< 6.1"
   gem "minitest-stub-const"
   gem "mocha", "~> 3.0"
 end