Update actions/checkout action to v4 (#176)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/conftest.yaml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v2
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
 
       - name: Conftest
         uses: redhat-cop/github-actions/confbatstest@master