Fix some Flax models' `hidden_states`
# What does this PR do?

Fix some Flax models where the last element in `hidden_states` is different between PT/Flax version.

## More context

Some models have 

```
last_hidden_state = self.layer_norm(last_hidden_state)
```

In Pytorch version, the returned `hidden_states` have this `last_hidden_state` (after layer norm) as the last element.
In Flax version, the last element of the returned `hidden_states` is the one before the layer norm.

This PR fixes this inconsistency (by using the PyTorch logic).


_The documentation is not available anymore as the PR was closed or merged._