Build: Bump cython from 3.1.5 to 3.1.6

Bumps [cython](https://github.com/cython/cython) from 3.1.5 to 3.1.6.
- [Release notes](https://github.com/cython/cython/releases)
- [Changelog](https://github.com/cython/cython/blob/master/CHANGES.rst)
- [Commits](cython/cython@3.1.5...3.1.6)

---
updated-dependencies:
- dependency-name: cython
  dependency-version: 3.1.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]