[skip-release] Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/push.yaml

@@ -7,7 +7,7 @@ jobs:
       contents: read
     runs-on: ubuntu-24.04
     steps:
-      - uses: actions/checkout@08c6903cd8c0fde910a37f88322edcfb5dd907a8 # v5
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6
       - run: shellcheck *.sh
   push:
     needs: [lint]