FIX: typo

git-svn-id: https://silverstripe-ecommerce.googlecode.com/svn/modules/ecommerce_tax/trunk@5225 950b781c-c544-efab-2f99-90083ee69683
git-svn-id: https://silverstripe-ecommerce.googlecode.com/svn/modules/ecommerce_tax/trunk@5236 950b781c-c544-efab-2f99-90083ee69683