Bump miminum cucumber version to 4

[mvz]

Summary

Bump miminum cucumber version to 4

Details

Update the mimimum required cucumber version to 4 in the gemspec; adjust Appraisals and GitHub Actions configuration.

Motivation and Context

Cucumber 4 is the first version using cucumber-gherkin instead of gherkin as a dependency. Using this as the lowest supported version avoids conflicts between gherkin and cucumber-gherkin when installing all appraisals.

How Has This Been Tested?

CI

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Internal change (refactoring, test improvements, developer experience or update of dependencies)

Checklist:

• I've added tests for my code
• My change requires a change to the documentation.
• I have updated the documentation accordingly.