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

📋 Checklist:

• [x] I agree to respect and uphold the Cucumber Community Code of Conduct
• [x] I've changed the behaviour of the code
  • [x] I have added/updated tests to cover my changes.
• [ ] My change requires a change to the documentation.
  • [ ] I have updated the documentation accordingly.
• [x] Users should know about my change
  • [x] I have added an entry to the "Unreleased" section of the CHANGELOG, linking to this pull request.

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[coveralls]

Coverage: 98.561%. Remained the same when pulling 2622e143739f6d81015fede02cd0d2c517366b53 on fix/2226 into 3811f811af61d6e7ed29ec2f31b1d2eabefc0a09 on main.