build: bump black from 25.12.0 to 26.3.1

Bumps [black](https://github.com/psf/black) from 25.12.0 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@25.12.0...26.3.1)

---
updated-dependencies:
- dependency-name: black
  dependency-version: 26.3.1
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

poetry.lock

@@ -50,7 +50,7 @@ rfc3987 = "^1.3.8"
 pytest = "^9.0.2"
 pytest-cov = "7.0.0"
 flake8 = "7.3.0"
-black = "25.12.0"
+black = "26.3.1"
 pre-commit = "4.5.1"
 pytest_httpserver = "1.1.5"
 trustme = "1.2.1"