Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/main.yml

@@ -15,7 +15,7 @@ jobs:
   docker:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3