Deleting recurring fee product feature doesn't remove entry in uc_recurring_products

When deleting a recurring fee from a product the entry is not removed from the uc_recurring_products table.

I believe this is because uc_recurring_product_features() incorrectly specifies the delete callback as 'uc_recurring_fee_delete' where it should be 'uc_recurring_fee_product_delete'.

Attached is a patch to fix this.