Remove unused notification kTabModelUserNavigatedNavigation.

ios/chrome/browser/tabs/tab_model.mm

 // Copyright 2012 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/tabs/tab_model.h"
 
 #include <cstdint>
 #include <utility>
 #include <vector>
 
@@ skipping 39 matching lines @@
 #include "ios/web/public/certificate_policy_cache.h"
 #include "ios/web/public/navigation_item.h"
 #import "ios/web/public/navigation_manager.h"
 #include "ios/web/public/web_thread.h"
 #import "ios/web/web_state/ui/crw_web_controller.h"
 #import "ios/web/web_state/web_state_impl.h"
 #include "url/gurl.h"
 
 NSString* const kTabModelTabWillStartLoadingNotification =
     @"kTabModelTabWillStartLoadingNotification";
-NSString* const kTabModelUserNavigatedNotification = @"kTabModelUserNavigation";
 NSString* const kTabModelTabDidStartLoadingNotification =
     @"kTabModelTabDidStartLoadingNotification";
 NSString* const kTabModelTabDidFinishLoadingNotification =
     @"kTabModelTabDidFinishLoadingNotification";
 NSString* const kTabModelAllTabsDidCloseNotification =
     @"kTabModelAllTabsDidCloseNotification";
 NSString* const kTabModelTabDeselectedNotification =
     @"kTabModelTabDeselectedNotification";
 NSString* const kTabModelNewTabWillOpenNotification =
     @"kTabModelNewTabWillOpenNotification";
@@ skipping 895 matching lines @@
 }
 
 // Called when UIApplicationWillEnterForegroundNotification is received.
 - (void)applicationWillEnterForeground:(NSNotification*)notify {
   if (_tabUsageRecorder) {
     _tabUsageRecorder->AppWillEnterForeground();
   }
 }
 
 @end