Update dependency flake8-bandit to v4

This MR contains the following updates:

Package	Type	Update	Change
flake8-bandit	dev-dependencies	major	^2.1.2 -> ^4.0.0

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Release Notes

tylerwince/flake8-bandit

v4.1.1

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pyproject.toml

@@ -52,7 +52,7 @@ isort = "^5.0.0"
 flake8 = "^3.8.2"
 flake8-black = "^0.2.0"
 flake8-mypy = "^17.8.0"
-flake8-bandit = "^2.1.2"
+flake8-bandit = "^4.0.0"
 flake8-isort = "^4.0.0"
 flake8-builtins = "^1.5.3"
 flake8-docstrings = "^1.5.0"