Bump ruff from 0.8.6 to 0.9.1

Bumps [ruff](https://github.com/astral-sh/ruff) from 0.8.6 to 0.9.1.
- [Release notes](https://github.com/astral-sh/ruff/releases)
- [Changelog](https://github.com/astral-sh/ruff/blob/main/CHANGELOG.md)
- [Commits](https://github.com/astral-sh/ruff/commits)

---
updated-dependencies:
- dependency-name: ruff
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements/mdformat.txt

@@ -19,4 +19,4 @@ mdformat_simple_breaks == 0.0.1
 mdformat_tables == 1.0.0
 mdformat-toc == 0.3.0
 mdformat-web == 0.2.0
-ruff == 0.8.6
+ruff == 0.9.1

requirements/ruff.txt

@@ -1 +1 @@
-ruff == 0.8.6
+ruff == 0.9.1