Bump black from 25.12.0 to 26.1.0 in /spiffe-tls (#374)

Bumps [black](https://github.com/psf/black) from 25.12.0 to 26.1.0.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](psf/black@25.12.0...26.1.0)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 26.1.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

spiffe-tls/poetry.lock

@@ -18,7 +18,7 @@ pyOpenSSL = ">=24,<26"
 idna = "^3.0"
 
 [tool.poetry.dev-dependencies]
-black = "^25.12"
+black = "^26.1"
 mypy = "^1.19"
 mypy-protobuf = "^5.0"
 types-pyOpenSSL = "^24.1"