Point httpcore2 project.urls at this repository

[Kludex]

The httpcore2 project.urls pointed at upstream encode/httpcore locations, which misdirected users browsing from PyPI. Update them to the pydantic/httpx2 repository, matching the convention already used in src/httpx2/pyproject.toml.

Closes #991

AI Disclaimer

This PR was developed with the assistance of either Claude or Codex. I've reviewed and verified the changes.

[github-actions]

Docs preview: https://41345017-httpx2-docs.pydantic.workers.dev

[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 7 skipped benchmarks¹

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_{Comparing fix-httpcore2-project-urls (d5e55c0) with main (0ba70ab)}

Footnotes

1. 7 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩