Revert of Set user agent type of transient item the same as pending item.

ios/web/navigation/navigation_manager_impl.mm

Index: ios/web/navigation/navigation_manager_impl.mm
diff --git a/ios/web/navigation/navigation_manager_impl.mm b/ios/web/navigation/navigation_manager_impl.mm
index d4d0857b74a54a31e56f18b4a34138c989c9abe8..da2ae03a14d715f438312e472af75142eecc141b 100644
--- a/ios/web/navigation/navigation_manager_impl.mm
+++ b/ios/web/navigation/navigation_manager_impl.mm
@@ -168,15 +168,6 @@
   WebState::OpenURLParams params(url, referrer,
                                  WindowOpenDisposition::CURRENT_TAB, type, NO);
   delegate_->GetWebState()->OpenURL(params);
-}
-
-void NavigationManagerImpl::AddTransientItem(const GURL& url) {
-  [session_controller_ addTransientItemWithURL:url];
-
-  // Transient item can only be added for pending non-app-specific loads.
-  DCHECK(GetPendingItem());
-  DCHECK_NE(UserAgentType::NONE, GetPendingItem()->GetUserAgentType());
-  GetTransientItem()->SetUserAgentType(GetPendingItem()->GetUserAgentType());
 }
 
 void NavigationManagerImpl::AddPendingItem(