Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/main.yml

@@ -12,7 +12,7 @@ jobs:
   Lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v6
         with:
           python-version: '3.8'