Upgrade Ruby to 3.4.1 and drop support for end-of-life versions

[Copilot]

This PR upgrades the project to use Ruby 3.4.1 (the latest stable release) and drops support for Ruby versions that are no longer officially maintained by the Ruby core team.

Changes Made

• Updated Ruby version files: .ruby-version and .tool-versions now specify Ruby 3.4.1
• Increased minimum Ruby requirement: Updated airports.gemspec from >= 2.6 to >= 3.1
• Modernized CI test matrix: Now only tests against Ruby 3.1, 3.2, 3.3, and 3.4 (removed 2.6, 2.7, 3.0)
• Updated RuboCop configuration: Set TargetRubyVersion to 3.1 and migrated to the modern plugins syntax
• Added changelog entry: Documented the upgrade in CHANGELOG.md for the upcoming v1.13.0 release

Rationale

This upgrade follows the project's established pattern of dropping support for Ruby versions that have reached end-of-life:

• Ruby 2.6: EOL since March 2022
• Ruby 2.7: EOL since April 2023
• Ruby 3.0: Approaching EOL in March 2024

By requiring Ruby 3.1+, users get access to modern Ruby features while the project maintains compatibility with all currently supported Ruby versions.

Testing

• ✅ All existing tests pass (23/23 examples)
• ✅ RuboCop linting passes with no offenses
• ✅ CodeQL security analysis shows no vulnerabilities
• ✅ No breaking changes to the public API

The upgrade is fully backward compatible for users running Ruby 3.1 or newer.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/ruby/ruby/releases
  • Triggering command: curl -s REDACTED (http block)
• https://api.github.com/repos/ruby/ruby/releases/latest
  • Triggering command: curl -s REDACTED (http block)
• www.ruby-lang.org
  • Triggering command: curl -s REDACTED (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.