clear some TODOs about SCN at storage layer

src/storage/compaction/ob_tablet_merge_task.cpp

@@ -617,7 +617,7 @@ int ObTabletMergePrepareTask::process()
       ret = OB_ERR_UNEXPECTED;
       LOG_ERROR("Unexcepted empty log ts range in minor merge", K(ret), K(ctx->scn_range_));
     } else {
-      ctx->merge_scn_ = ctx->scn_range_.end_scn_.get_val_for_inner_table_field();
+      ctx->merge_scn_ = ctx->scn_range_.end_scn_;
     }
   }