Bump ruff from 0.6.3 to 0.6.8

Bumps [ruff](https://github.com/astral-sh/ruff) from 0.6.3 to 0.6.8.
- [Release notes](https://github.com/astral-sh/ruff/releases)
- [Changelog](https://github.com/astral-sh/ruff/blob/main/CHANGELOG.md)
- [Commits](astral-sh/ruff@0.6.3...0.6.8)

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

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

Author: dependabot[bot]

requirements.txt

@@ -2,4 +2,4 @@
 numpy==2.1.1
 pytest==8.3.3
 pytest-cov==5.0.0
-ruff==0.6.3
+ruff==0.6.8