[BugFix] Use GitHub for flake8 pre-commit hook (#679)

Author: vmoens

.pre-commit-config.yaml

@@ -18,7 +18,7 @@ repos:
           - black == 21.9b0
           - usort == 0.6.4
 
-  - repo: https://gitlab.com/pycqa/flake8
+  - repo: https://github.com/pycqa/flake8
     rev: 3.9.2
     hooks:
       - id: flake8