Delete the NTPPreferAmpUrls feature flag.

components/ntp_snippets/features.h

 // 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 COMPONENTS_NTP_SNIPPETS_FEATURES_H_
 #define COMPONENTS_NTP_SNIPPETS_FEATURES_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 19 matching lines @@
 // TODO(jkrcal): Rename to kRemoteSuggestionsFeature.
 extern const base::Feature kArticleSuggestionsFeature;
 extern const base::Feature kBookmarkSuggestionsFeature;
 extern const base::Feature kRecentOfflineTabSuggestionsFeature;
 extern const base::Feature kPhysicalWebPageSuggestionsFeature;
 extern const base::Feature kForeignSessionsSuggestionsFeature;
 
 // Feature to allow UI as specified here: https://crbug.com/660837.
 extern const base::Feature kIncreasedVisibility;
 
-// Feature to prefer AMP URLs over regular URLs when available.
-extern const base::Feature kPreferAmpUrlsFeature;
-
 // Feature to listen for GCM push updates from the server.
 extern const base::Feature kContentSuggestionsPushFeature;
 
 // Feature to choose a category ranker.
 extern const base::Feature kCategoryRanker;
 
 // Feature to allow the new Google favicon server for fetching publisher icons.
 extern const base::Feature kPublisherFaviconsFromNewServerFeature;
 
 // Parameter and its values for the kCategoryRanker feature flag.
@@ skipping 59 matching lines @@
 constexpr int kNotificationsDefaultDailyLimit = 1;
 
 // An integer. The number of notifications that can be ignored. If the user
 // ignores this many notifications or more, we stop sending them.
 extern const char kNotificationsIgnoredLimitParam[];
 constexpr int kNotificationsIgnoredDefaultLimit = 3;
 
 }  // namespace ntp_snippets
 
 #endif  // COMPONENTS_NTP_SNIPPETS_FEATURES_H_