Fix flake8 pre-commit hook.

Author: Diptorup Deb

.pre-commit-config.yaml

@@ -31,7 +31,7 @@ repos:
     -   id: isort
         name: isort (cython)
         types: [cython]
--   repo: https://gitlab.com/pycqa/flake8
+-   repo: https://github.com/pycqa/flake8
     rev: 3.9.2
     hooks:
     -   id: flake8