Remove unused action on the before_action callback.

```
The update action could not be found for the :load_order
callback on Spree::Admin::OrdersController, but it is listed in the controller's
:only option.

Raising for missing callback actions is a new default in Rails 7.1, if you'd
like to turn this off you can delete the option from the environment configurations
or set `config.action_pack.raise_on_missing_callback_actions` to `false`.
```

backend/app/controllers/spree/admin/orders_controller.rb

@@ -4,7 +4,7 @@ module Spree
   module Admin
     class OrdersController < Spree::Admin::BaseController
       before_action :initialize_order_events
-      before_action :load_order, only: [:edit, :update, :complete, :advance, :cancel, :resume, :approve, :resend, :unfinalize_adjustments, :finalize_adjustments, :cart, :confirm]
+      before_action :load_order, only: [:edit, :complete, :advance, :cancel, :resume, :approve, :resend, :unfinalize_adjustments, :finalize_adjustments, :cart, :confirm]
       around_action :lock_order, only: [:update, :advance, :complete, :confirm, :cancel, :resume, :approve, :resend]
 
       rescue_from Spree::Order::InsufficientStock, with: :insufficient_stock_error