Bump black from 26.1.0 to 26.3.1 in /requirements

Bumps [black](https://github.com/psf/black) from 26.1.0 to 26.3.1.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/main/CHANGES.md)
- [Commits](https://github.com/psf/black/compare/26.1.0...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>

requirements/dev-requirements.txt

@@ -1,4 +1,4 @@
 -r requirements.txt
-black==26.1.0
+black==26.3.1
 ipdb==0.13.13
 pygraphviz==1.14