fix: docs workflow should fail if out-of-date

Signed-off-by: Vladislav Doster <[email protected]>

.github/workflows/documentation.yaml

@@ -26,5 +26,5 @@ jobs:
       - name: check for out-of-date documentation
         run: |
           if ! git --no-pager diff --exit-code; then
-            echo "::set-output zshelldocs are out-of-date, run 'make doc'"
+            echo "::error Z-shelldocs are out-of-date. To regenerate, run 'make doc'"
           fi