Cleanup ContentSuggestions, removing unused functions

ios/chrome/browser/content_suggestions/content_suggestions_mediator.mm

 // Copyright 2017 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.
 
 #import "ios/chrome/browser/content_suggestions/content_suggestions_mediator.h"
 
 #include "base/mac/bind_objc_block.h"
 #include "base/memory/ptr_util.h"
 #include "base/optional.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/ntp_snippets/category.h"
 #include "components/ntp_snippets/content_suggestion.h"
 #import "ios/chrome/browser/content_suggestions/content_suggestions_category_wrapper.h"
 #import "ios/chrome/browser/content_suggestions/content_suggestions_service_bridge_observer.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestion.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_data_sink.h"
-#import "ios/chrome/browser/ui/content_suggestions/content_suggestions_item.h"
 #import "ios/chrome/browser/ui/content_suggestions/content_suggestions_section_information.h"
 #include "ui/gfx/image/image.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace {
 
 // Returns the Type for this |category|.
@@ skipping 170 matching lines @@
       self.contentService->GetCategoryInfo(category);
 
   ContentSuggestionsSectionInformation* sectionInfo =
       SectionInformationFromCategoryInfo(categoryInfo, category);
 
   self.sectionInformationByCategory[[ContentSuggestionsCategoryWrapper
       wrapperWithCategory:category]] = sectionInfo;
 }
 
 @end