[enhancement](load) avoid schema copy to reduce cpu usage (#16034)

be/src/runtime/tablets_channel.cpp

@@ -242,7 +242,7 @@ Status TabletsChannel::_open_all_writers(const PTabletWriterOpenRequest& request
         wrequest.tuple_desc = _tuple_desc;
         wrequest.slots = index_slots;
         wrequest.is_high_priority = _is_high_priority;
-        wrequest.ptable_schema_param = request.schema();
+        wrequest.table_schema_param = _schema;
 
         DeltaWriter* writer = nullptr;
         auto st = DeltaWriter::open(&wrequest, &writer, _load_id);