Removes two unnecessary cells + adds missing unit test for an existing cell

ios/chrome/browser/payments/cells/order_summary_line_item.h

Index: ios/chrome/browser/payments/cells/order_summary_line_item.h
diff --git a/ios/chrome/browser/payments/cells/order_summary_line_item.h b/ios/chrome/browser/payments/cells/order_summary_line_item.h
deleted file mode 100644
index 01e87f3d9104fd0483371caa490f228b0d6fec90..0000000000000000000000000000000000000000
--- a/ios/chrome/browser/payments/cells/order_summary_line_item.h
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright 2016 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef IOS_CHROME_BROWSER_PAYMENTS_CELLS_ORDER_SUMMARY_LINE_ITEM_H_
-#define IOS_CHROME_BROWSER_PAYMENTS_CELLS_ORDER_SUMMARY_LINE_ITEM_H_
-
-#import <UIKit/UIKit.h>
-
-#import "ios/chrome/browser/ui/collection_view/cells/collection_view_detail_item.h"
-
-// OrderSummaryLineItem is the model class for a CollectionViewDetailItem with
-// custom font properties.
-@interface OrderSummaryLineItem : CollectionViewDetailItem
-
-@end
-
-#endif  // IOS_CHROME_BROWSER_PAYMENTS_CELLS_ORDER_SUMMARY_LINE_ITEM_H_