[Ruby] Minimum version bump

[luke-hill]

🤔 What's changed?

Bump minimum versions of gems/ruby
Remove lots of crud that supported old rubies

⚡️ What's your motivation?

Tidy up codebase

🏷️ What kind of change is this?

• 🏦 Refactoring/debt/DX (improvement to code design, tooling, documentation etc. without changing behaviour)

♻️ Anything particular you want feedback on?

📋 Checklist:

• I agree to respect and uphold the Cucumber Community Code of Conduct
• I've changed the behaviour of the code
  • I have added/updated tests to cover my changes.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly.
• Users should know about my change
  • I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d41178f) 91.17% compared to head (e4040ce) 91.17%.
Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #228   +/-   ##
=======================================
  Coverage   91.17%   91.17%           
=======================================
  Files           2        2           
  Lines          34       34           
=======================================
  Hits           31       31           
  Misses          3        3           

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