Update bandit requirement from >=1.5.1 to >=1.8.6

Updates the requirements on [bandit](https://github.com/PyCQA/bandit) to permit the latest version.
- [Release notes](https://github.com/PyCQA/bandit/releases)
- [Commits](PyCQA/bandit@1.5.1...1.8.6)

---
updated-dependencies:
- dependency-name: bandit
  dependency-version: 1.8.6
  dependency-type: direct:development
...

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

Author: dependabot[bot]

dev-requirements.txt

@@ -1,6 +1,6 @@
 setuptools>=40.8.0
 vulture>=1.0
-bandit>=1.5.1
+bandit>=1.8.6
 pydocstyle>=3.0.0
 pytest>=4.3.1
 pytest-cov>=2.6.1