ci: update Ruby from 3.4 to 4.0

[aguynamedryan]

Summary

• Update CI workflow to use Ruby 4.0

Test plan

• CI should pass with Ruby 4.0

🤖 Generated with Claude Code

Summary by CodeRabbit

• Chores
  • CI test workflow updated to use Ruby 4.0.
  • Development dependency on Bundler relaxed to allow any version >= 2.0.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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Walkthrough

CI workflow ruby/setup-ruby version bumped from 3.4 to 4.0; gemspec development dependency for bundler loosened from "~> 2.0" to ">= 2.0".

Changes

Cohort / File(s)	Summary
CI Configuration ​.github/workflows/run_tests.yml	Bumped ruby-version in the ruby/setup-ruby step of the Run-Spark-Tests job from 3.4 to 4.0.
Packaging / Gemspec conceptql.gemspec	Relaxed development dependency on bundler from ~> 2.0 to >= 2.0, removing the upper bound.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• ci: update Spark job Ruby from 3.2 to 3.3 #320: Modifies the same CI workflow Run-Spark-Tests job ruby/setup-ruby step to bump the Ruby version.

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'ci: update Ruby from 3.4 to 4.0' directly and accurately reflects the main change in the pull request—updating the Ruby version in the CI workflow.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch ruby-4.0-upgrade

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