Changed actions checkout for protected files to v3

Author: briantkim-msft

.github/workflows/protected-files.yaml

@@ -21,7 +21,7 @@ jobs:
         if: ${{ env.user-allowed == 'true' }}
         run: echo "Account '${{ github.event.pull_request.user.login }}' is allowed to update protected files"
 
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v3
         if: ${{ env.user-allowed != 'true' }}
         with:
           # Required since "HEAD^" is passed to Get-ChangedFiles