Add explanation for async state updates not needing to be wrapped in act()

Author: aryyya

docs/usage/advanced-hooks.md

@@ -132,6 +132,10 @@ test('should increment counter after delay', async () => {
 })
 ```
 
+Wrapping `incrementAsync` in `act()` is not necessary since the state updates happen
+asynchronously during `await waitForNextUpdate()`. The async utils automatically wrap the waiting
+code in the asynchronous `act()` wrapper.
+
 For more details on the the other async utilities, please refer to the
 [API Reference](/reference/api#async-utilities).