Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/dependabot-automerge.yml

@@ -7,7 +7,7 @@ jobs:
   auto-merge:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: ahmadnassri/action-dependabot-auto-merge@v2
         with:
           config: .github/dependabot-automerge-config.yml