Use Multiple Expressions In Select List
Try changing your * with just the column name. Although it means the same, now it should be clear to SQL Server:

SELECT
    [StoreName] = (SELECT storename
                     FROM OPENQUERY(192.168.5.812, 'SELECT storename
                                    FROM stores') x
                    WHERE x.storename = y.storename)
    [StoreManager] = y.storemanager
FROM 
    managerinfo y ;