troute.network: handle fiona dependency for geopandas>=1.0.0

[program--]

This PR adds fiona to the troute.network dependencies to handle the case when consumers have geopandas>=1.0.0 without explicitly installing fiona. This change shouldn't impact consumers with geopandas<1.0.0, since fiona will already be installed.

Additions

• Adds fiona to troute.network's pyproject.toml dependencies

Checklist

• PR has an informative and human-readable title
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• Passes all existing automated tests
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• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
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