Fix pending migration check for Rails 7.2

Rails 7.2 removed migration_context from ActiveRecord::Base.connection

core/lib/spree/testing_support/dummy_app/migrations.rb

@@ -4,19 +4,12 @@ module DummyApp
   module Migrations
     extend self
 
-    # Ensure database exists
-    def database_exists?
-      ActiveRecord::Base.connection
-    rescue ActiveRecord::NoDatabaseError
-      false
-    else
-      true
-    end
-
     def needs_migration?
-      return true if !database_exists?
-
-      ActiveRecord::Base.connection.migration_context.needs_migration?
+      ActiveRecord::Migration.check_all_pending!
+    rescue ActiveRecord::PendingMigrationError, ActiveRecord::NoDatabaseError
+      true
+    else
+      false
     end
 
     def auto_migrate