[iOS] Removing useless instance variable in PrivateTableViewController

Removing _prefChangeRegistrarApplicationContext from
PrivateTableViewController. This should have been done in:
crrev.com/c/1798709

Bug: 951313
Change-Id: I4288d6f830197e4c8e326e752bc6aac779ead7c3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829702
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#701499}

ios/chrome/browser/ui/settings/privacy_table_view_controller.mm

@@ -67,7 +67,6 @@ GURL kGoogleServicesSettingsURL("settings://open_google_services");
   std::unique_ptr<PrefObserverBridge> _prefObserverBridge;
   // Registrar for pref changes notifications.
   PrefChangeRegistrar _prefChangeRegistrar;
-  PrefChangeRegistrar _prefChangeRegistrarApplicationContext;
 
   // Updatable Items
   TableViewDetailIconItem* _handoffDetailItem;
@@ -94,8 +93,6 @@ GURL kGoogleServicesSettingsURL("settings://open_google_services");
     PrefService* prefService = _browserState->GetPrefs();
 
     _prefChangeRegistrar.Init(prefService);
-    _prefChangeRegistrarApplicationContext.Init(
-        GetApplicationContext()->GetLocalState());
     _prefObserverBridge.reset(new PrefObserverBridge(self));
     // Register to observe any changes on Perf backed values displayed by the
     // screen.