fix formatting of code snippet

Signed-off-by: Alexander Müller <[email protected]>

Author: alexanderdd

admin_manual/occ_command.rst

@@ -250,7 +250,7 @@ enabled or disabled::
 
  sudo -E -u www-data php occ app:list
 
-List all of your installed and enabled (flag --enabled) or disabled (flag --disabled) apps::
+List all of your installed and enabled (flag `--enabled`) or disabled (flag `--disabled`) apps::
 
  sudo -E -u www-data php occ app:list --enabled