Out of date sentence in `01-quickstart`

[vshakitskiy]

Before What next section, there is small hint section, saying:

Depending on your network speed, you might notice that when you add a new cat the last cat image is duplicated for a moment before the new one appears. While we won’t touch on it in this guide, you can learn more about why this happens and how to prevent it in the rendering lists hint.

The quickstart uses list.append now, image duplicating no longer appears. The sentence above and a small part inside hint that describes quickstart's example should probably be rewritten