chore(deps): bump black in /python/framework-extensions/strands-agents

Bumps [black](https://github.com/psf/black) from 25.1.0 to 26.3.1.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](psf/black@25.1.0...26.3.1)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 26.3.1
  dependency-type: indirect
...

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Author: dependabot[bot]