Remove manually disable field trail feature

Make sure brave/brave-browser#4551 and
#2471 landed first

app/brave_main_delegate.cc

@@ -28,7 +28,6 @@
 #include "components/autofill/core/common/autofill_payments_features.h"
 #include "components/omnibox/common/omnibox_features.h"
 #include "components/password_manager/core/common/password_manager_features.h"
-#include "components/sync/driver/sync_driver_switches.h"
 #include "components/unified_consent/feature.h"
 #include "extensions/common/extension_features.h"
 #include "services/network/public/cpp/features.h"
@@ -160,9 +159,6 @@ bool BraveMainDelegate::BasicStartupComplete(int* exit_code) {
   // Disabled features.
   const std::unordered_set<const char*> disabled_features = {
       autofill::features::kAutofillServerCommunication.name,
-      // TODO(darkdh): remove this when USS bookmarks is mature
-      // 84919fdb99b162030a1113d5990667885b774064
-      switches::kSyncUSSBookmarks.name,
       network::features::kNetworkService.name,
       unified_consent::kUnifiedConsent.name,
   };