Update repository URL for Flake8 (#1994)

Committed via https://github.com/asottile/all-repos

Author: jugmac00

.pre-commit-config.yaml

@@ -46,7 +46,7 @@ repos:
         args:
           - --min-py3-version
           - "3.4"
-  - repo: https://gitlab.com/pycqa/flake8
+  - repo: https://github.com/PyCQA/flake8
     rev: 3.9.0
     hooks:
       - id: flake8