Update managing-complex-workflows.md (#762)

Co-authored-by: Lucas Costi <[email protected]>

Author: gsrohde

content/actions/learn-github-actions/managing-complex-workflows.md

@@ -24,12 +24,13 @@ This example action demonstrates how to reference an existing secret as an envir
 ```yaml
 jobs:
   example-job:
+    runs-on: ubuntu-latest
     steps:
       - name: Retrieve secret
         env:
           super_secret: ${{ secrets.SUPERSECRET }}
         run: |
-          example-command "$SUPER_SECRET"
+          example-command "$super_secret"
 ```
 {% endraw %}