Merge pull request #76 from nationalarchives/renovate/actions-checkout-4.x

Update actions/checkout action to v4

Author: jacksonj04

.github/workflows/secrets.yml

@@ -7,5 +7,5 @@ jobs:
     name: Check for secrets
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: nationalarchives/tdr-github-actions/.github/actions/run-git-secrets@main