ci: change pre-commit hook repo of flake8

https://gitlab.com/pycqa/flake8 is not available.

Author: utgwkk

.pre-commit-config.yaml

@@ -19,7 +19,7 @@ repos:
   hooks:
   - id: check-manifest
 
-- repo: https://gitlab.com/pycqa/flake8
+- repo: https://github.com/PyCQA/flake8
   rev: 3.8.3
   hooks:
   - id: flake8