Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/policy.yaml

@@ -9,6 +9,6 @@ jobs:
   policy:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@2541b1294d2704b0964813337f33b291d3f8596b # tag=v3.0.2
+      - uses: actions/checkout@a5ac7e51b41094c92402da3b24376905380afc29 # v4.1.6
       - uses: docker://ghcr.io/policy-as-versioned-code/policy-checker:latest