Bump vws-python to 2026.2.21

[adamtheturtle]

Summary

• Bump vws-python from 2026.2.15 to 2026.2.21 in pyproject.toml
• Add the new required content parameter to all Response constructor calls in tests to match the updated API

🤖 Generated with Claude Code

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Note

Low Risk
Primarily a dependency bump plus test-only updates to satisfy a new Response constructor requirement; no production logic changes.

Overview
Bumps the vws-python dev dependency from 2026.2.15 to 2026.2.21.

Updates test helpers and query endpoint tests to pass the newly-required content argument when constructing vws.response.Response, keeping the test suite compatible with the updated vws-python API.

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