chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/flake8.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-22.04
 
     steps:
-      - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6
 
       - name: Set up Python
         uses: actions/setup-python@v5