Upgrade to latest ruby

[bess]

Currently, our ruby build is 3.1 which is near its end of life.

Acceptance Criteria

• [x] .tool-versions
• [ ] CircleCI
• [ ] ansible
• [ ] github pages (.github)

Note: tried twice in June 2024, too many test failures to proceed easily. Ruby 3.1 support ends 31 Mar 2025. Let's get to this by then.

[kelynch]

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