Supplier has been added to the Edit Wine screen so you can change a Wine's supplier. This will impact invoicing (such that wine will be broken out onto a different supplier order) so you should not be changing a Wines supplier unless you have a known reason to do so. However, there is sometimes a legitimate need to re-assign Supplier you can now accomplish this!
Steps to edit supplier
Navigate to the wines tab
Select the wine you would like to reassign the supplier for
On the left hand side, click the red re-assign supplier link
Select the new supplier you would like from the dropdown menu
Click the blue save button