Bump isort from 5.9.0 to 5.9.1

Bumps [isort](https://github.com/pycqa/isort) from 5.9.0 to 5.9.1.
- [Release notes](https://github.com/pycqa/isort/releases)
- [Changelog](https://github.com/PyCQA/isort/blob/main/CHANGELOG.md)
- [Commits](PyCQA/isort@5.9.0...5.9.1)

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

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

Author: dependabot[bot]

linter-requirements.txt

@@ -1,5 +1,5 @@
 bandit==1.7.0
 black==21.6b0
 flake8==3.9.2
-isort==5.9.0
+isort==5.9.1
 pydocstyle==6.1.1