Switch flake8 from gitlab to github (#287)

.pre-commit-config.yaml

@@ -10,7 +10,7 @@ repos:
       - id: codespell
         args:
           - --ignore-words-list=linz
-  - repo: https://gitlab.com/PyCQA/flake8
+  - repo: https://github.com/PyCQA/flake8
     rev: 4.0.1
     hooks:
       - id: flake8