chore(deps): update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/terraform-docs.yaml

@@ -5,7 +5,7 @@ jobs:
   docs:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
       with:
         ref: ${{ github.event.pull_request.head.ref }}