chore: add missing pytz dependency

[davidgamez]

Summary:

The pytz package is no longer available in the latest Python runtime on GitHub Actions. This PR adds the dependency.
This fixing actions like: https://github.com/MobilityData/mobility-feed-api/actions/runs/21216247449/job/61040991169

Expected behavior:

GitHub actions pass without incident.

Testing tips:

Build must pass.

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• Run the unit tests with ./scripts/api-tests.sh to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
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