Ignore unexpected weights from PT conversion
Some weights resulting from the conversion from a PyTorch model to a TensorFlow model are throwing an unnecessary warning.

To see for yourself, the following code throws a warning before the PR:

```py
from transformers import BertForPreTraining, BertConfig, TFBertForPreTraining

pt = BertForPreTraining(BertConfig())
pt.save_pretrained("here")
tf = TFBertForPreTraining.from_pretrained("here", from_pt=True)
```

Fix https://github.com/huggingface/transformers/issues/10348