Update test-kitchen requirement from ~> 1.16.0 to ~> 1.25.0

Updates the requirements on [test-kitchen](https://github.com/test-kitchen/test-kitchen) to permit the latest version.
- [Release notes](https://github.com/test-kitchen/test-kitchen/releases)
- [Changelog](https://github.com/test-kitchen/test-kitchen/blob/v1.25.0/CHANGELOG.md)
- [Commits](test-kitchen/test-kitchen@v1.16.0...v1.25.0)

Author: dependabot-preview[bot]

sensu-plugins-postgres.gemspec

@@ -53,6 +53,6 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec',                     '~> 3.1'
   s.add_development_dependency 'rubocop',                   '~> 0.79.0'
   s.add_development_dependency 'serverspec',                '~> 2.41.5'
-  s.add_development_dependency 'test-kitchen',              '~> 1.16.0'
+  s.add_development_dependency 'test-kitchen',              '~> 1.25.0'
   s.add_development_dependency 'yard',                      '~> 0.9.11'
 end