[pre-commit.ci] pre-commit autoupdate (#21)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: pre-commit-ci[bot]

.pre-commit-config.yaml

@@ -20,7 +20,7 @@ repos:
       - id: blackdoc
 
   - repo: https://github.com/PyCQA/flake8
-    rev: 3.9.2
+    rev: 4.0.1
     hooks:
       - id: flake8