chore: Add latest Rubies to CI matrix

[willnet]

• Add Ruby 3.2, 3.3, 3.4 and JRuby 9.4, 10.0 to CI matrix
• Remove JRuby 9.2 from CI matrix since setup-ruby on Ubuntu 24.4 only provides builds for JRuby 9.4 and later.
• Update actions/checkout to the latest
• Fix a failing test and a lint error

Checklist

• [x] I acknowledge that all my contributions will be made under the project's license
• [ ] I have made a material change to the repo (functionality, testing, spelling, grammar)
• [x] I have read the Contribution Guidelines and my PR follows them
• [x] I have titled the PR appropriately
• [x] I have updated my branch with the main branch
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added the necessary documentation about the functionality in the appropriate .md file
• [ ] I have added inline documentation to the code I modified

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