Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/ci.yml

@@ -9,6 +9,6 @@ jobs:
   policy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@a12a3943b4bdde767164f792f33f40b04645d846 # tag=v3.0.0
+      - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
       - uses: docker://ghcr.io/example-policy-org-demo/policy-checker:latest