build(deps): bump isort from 6.0.0 to 6.0.1 in /lib/spack/docs (#49213)

Bumps [isort](https://github.com/PyCQA/isort) from 6.0.0 to 6.0.1.
- [Release notes](https://github.com/PyCQA/isort/releases)
- [Changelog](https://github.com/PyCQA/isort/blob/main/CHANGELOG.md)
- [Commits](https://github.com/PyCQA/isort/compare/6.0.0...6.0.1)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

lib/spack/docs/requirements.txt

@@ -7,7 +7,7 @@ docutils==0.21.2
 pygments==2.19.1
 urllib3==2.3.0
 pytest==8.3.4
-isort==6.0.0
+isort==6.0.1
 black==25.1.0
 flake8==7.1.2
 mypy==1.11.1