fix code block in docs

docs/serving_iop4_in_production.rst

@@ -74,6 +74,7 @@ working in a linux system. Other OS provide different methods to create jobs.
 
 Use ``crontab -e`` to edit your crontab file and add a line like the following
 .. code-block:: cron
+  
       00 08 * * * /home/vhega/run_iop4_daily.sh > /home/vhega/run_iop4_daily.log 2>&1
 
 Then, create a file ``run_iop4_daily.sh``, give it execution permissions (``chmod +x run_iop4_daily.sh``) and add the following content: