Update Mage_Checkout.csv

As far as I understand this it is because the corresponding template (success.phtml) already replaces the \’ during interpretation. See http://www.magentocommerce.com/boards/viewthread/7301/ for more details
Update Mage_Checkout.csv

Forgot to replace it in the German translation, too.
Merge pull request #114 from nickw108/patch-1

Update Mage_Checkout.csv