fix: ensure feature paths are properly deduplicated

[davidjgoss]

🤔 What's changed?

Deduplicate feature paths a bit later in the process of expanding and normalizing them. This ensures that e.g. two overlapping glob expressions, or a mixture of a glob and a specific path, won't cause the same feature to be loaded multiple times.

⚡️ What's your motivation?

Fixes #2226

🏷️ What kind of change is this?

• 🐛 Bug fix (non-breaking change which fixes a defect)

📋 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.

---

This text was originally generated from a template, then edited by hand. You can modify the template here.

[coveralls]

Coverage: 98.561%. Remained the same when pulling 2622e14 on fix/2226 into 3811f81 on main.