Remove unused app config options

This has been defined in ENV for a while

app/models/spree/app_configuration.rb

@@ -33,9 +33,6 @@ module Spree
     preference :allow_backorder_shipping, :boolean, default: false
     preference :allow_checkout_on_gateway_error, :boolean, default: false
     preference :allow_guest_checkout, :boolean, default: true
-    # Replace with the name of a zone if you would like to limit the countries
-    preference :checkout_zone, :string, default: nil
-    preference :currency, :string, default: "USD"
     preference :currency_decimal_mark, :string, default: "."
     preference :currency_symbol_position, :string, default: "before"
     preference :currency_thousands_separator, :string, default: ","

db/migrate/20250103043626_delete_checkout_zone_and_currency_preferences.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class DeleteCheckoutZoneAndCurrencyPreferences < ActiveRecord::Migration[7.0]
+  def up
+    execute <<~SQL
+      DELETE FROM spree_preferences
+      WHERE key IN (
+        '/spree/app_configuration/checkout_zone',
+        '/spree/app_configuration/currency'
+      )
+    SQL
+  end
+end