Fix spacing at top of OrderShipping#ship method

Newest version of Rubocop wants us to remove extra spacing at the top of
method bodies.

(cherry picked from commit 6d44a13)

core/app/models/spree/order_shipping.rb

@@ -44,7 +44,6 @@ def ship_shipment(shipment, external_number: nil, tracking_number: nil, suppress
   # @return The carton created.
   def ship(inventory_units:, stock_location:, address:, shipping_method:,
            shipped_at: Time.current, external_number: nil, tracking_number: nil, suppress_mailer: false)
-
     carton = nil
 
     Spree::InventoryUnit.transaction do