Update indexeddb_todo_list.js

For the new IndexDB API, Deprecated interfaces and the changes of the IDBOpenDBRequest API, the onsuccess and oncomplete events. detail at the https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API  Deprecated interfaces section, and the demo of the https://developer.mozilla.org/en-US/docs/Web/API/IDBOpenDBRequest