pre-commit: autoupdate hook versions (#87)

Co-authored-by: keewis <[email protected]>

Author: github-actions[bot]

.pre-commit-config.yaml

@@ -22,6 +22,6 @@ repos:
     hooks:
       - id: blackdoc
   - repo: https://gitlab.com/pycqa/flake8
-    rev: 3.8.4
+    rev: 3.9.0
     hooks:
       - id: flake8