code: fix typo (#76)

* Update ob_dtl_rpc_channel.cpp

* Update ob_time_convert.cpp

* Update ob_time_convert.h

* Update ob_expr_date_add.cpp

* fix log spell error:faild -> failled, Faild -> Failed

* Update ob_optimizer_util.cpp

* Update ob_sql.cpp

* Update ob_optimizer_util.cpp

* Update ob_plan_cache_manager.cpp

* Update ob_partition_merge_task.cpp

src/sql/plan_cache/ob_plan_cache_manager.cpp

@@ -411,7 +411,7 @@ void ObPlanCacheManager::ObPlanCacheEliminationTask::run_free_cache_obj_task()
             ObCacheObject* to_del_obj = NULL;
             for (int j = 0; j < deleted_objs.count(); j++) {
               if (OB_FAIL(ObCacheObjectFactory::destroy_cache_obj(true, deleted_objs.at(j).obj_id_, plan_cache))) {
-                LOG_WARN("failde to destroy cache obj", K(ret));
+                LOG_WARN("failed to destroy cache obj", K(ret));
               }
             }  // end inner loop
           }