ci(docfx): Added checkout step for deployment

Author: r-dh

.github/workflows/docdeploy.yml

@@ -33,6 +33,11 @@ jobs:
     needs: build
     runs-on: ubuntu-latest # Required by 'JamesIves/github-pages-deploy-action'
     steps:
+      - name: Checkout
+        uses: actions/checkout@v2.3.1 # If you're using actions/checkout@v2 you must set persist-credentials to false in most cases for the deployment to work correctly.
+        with:
+          persist-credentials: false
+
       # Download the generated documentation
       - name: Download site artifact
         uses: actions/download-artifact@v1