Bump black from 25.12.0 to 26.3.1 in /requirements

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:production
...

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

Author: dependabot[bot]

requirements/lint.txt

@@ -1,3 +1,3 @@
-black==25.12.0
+black==26.3.1
 flake8==7.3.0
 isort==7.0.0