fix: update mocha config to avoid test timeouts

[davidjgoss]

🤔 What's changed?

Increase mocha timeout from 2s to 5s. We don't routinely have tests timeout so this should not make the build any slower in general.

⚡️ What's your motivation?

Fixes #2234. One or two API tests are doing multiple test runs and that's taking them over the 2s timeout on Windows sometimes. I expect we'll do more of this kind of test (i.e. using the runCucumber API) so don't want to just do it on a test by test basis.

🏷️ What kind of change is this?

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

📋 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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[coveralls]

Coverage: 98.564%. Remained the same when pulling 76e16ae on fix/flaky-api-tests into 847f613 on main.