uc_product_node_access() is invalid and should be removed

uc_product_node_access() in 7.x was renamed from uc_product_access() in 6.x, but the permissions it checks such as "create products", "edit all products", "edit own products", "delete all products", "delete own products", and variants for product classes, simply do not exist. Instead node.module handles all permission checks for product content in 7.x. This is documented at https://drupal.org/node/224333#hook_node_access but must have been overlooked in the 6>7 upgrade process.