build: Switch to github flake8 repo (#66)

Author: ptiurin

.pre-commit-config.yaml

@@ -38,7 +38,7 @@ repos:
     hooks:
       - id: black_nbconvert
 
-  - repo: https://gitlab.com/pycqa/flake8
+  - repo: https://github.com/PyCQA/flake8
     rev: 3.7.9
     hooks:
       - id: flake8