Update kitchen-dokken requirement from ~> 2.19.0 to ~> 2.20.3

Updates the requirements on [kitchen-dokken](https://github.com/test-kitchen/kitchen-dokken) to permit the latest version.
- [Release notes](https://github.com/test-kitchen/kitchen-dokken/releases)
- [Changelog](https://github.com/test-kitchen/kitchen-dokken/blob/main/CHANGELOG.md)
- [Commits](test-kitchen/kitchen-dokken@v2.19.0...v2.20.3)

---
updated-dependencies:
- dependency-name: kitchen-dokken
  dependency-type: direct:development
...

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

Gemfile

@@ -7,7 +7,7 @@ gem "rubocop-discourse"
 gem "rake"
 
 group :integration do
-  gem "kitchen-dokken", "~> 2.19.0"
+  gem "kitchen-dokken", "~> 2.20.3"
 end
 
 group :vagrant do