Bump httpx2 from 2.5.0 to 2.12.0

Bumps [httpx2](https://github.com/pydantic/httpx2) from 2.5.0 to 2.12.0.
- [Release notes](https://github.com/pydantic/httpx2/releases)
- [Changelog](https://github.com/pydantic/httpx2/blob/main/src/httpx2/CHANGELOG.md)
- [Commits](pydantic/httpx2@v2.5.0...v2.12.0)

---
updated-dependencies:
- dependency-name: httpx2
  dependency-version: 2.12.0
  dependency-type: direct:production
...

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Author: dependabot[bot]