Revert of [sync] Fix decryption failure caused by missing user_key

components/sync/engine_impl/model_type_worker_unittest.cc

Index: components/sync/engine_impl/model_type_worker_unittest.cc
diff --git a/components/sync/engine_impl/model_type_worker_unittest.cc b/components/sync/engine_impl/model_type_worker_unittest.cc
index cc4fd1bd2ff812e13ede75e9229d9a52bf6ddd15..486afe1e84f4dca1c8eb40bd12d2391452595562 100644
--- a/components/sync/engine_impl/model_type_worker_unittest.cc
+++ b/components/sync/engine_impl/model_type_worker_unittest.cc
@@ -216,8 +216,7 @@
       sync_pb::NigoriKey* key = bag.add_key();
 
       key->set_name(GetNigoriName(nigori));
-      nigori.ExportKeys(key->mutable_user_key(), key->mutable_encryption_key(),
-                        key->mutable_mac_key());
+      nigori.ExportKeys(key->mutable_encryption_key(), key->mutable_mac_key());
     }
 
     // Re-create the last nigori from that loop.