fix warnings in deberta
# What does this PR do?

In recent torch versions, the following warning is thrown on the deberta code:
```
 UserWarning: To copy construct from a tensor, it is recommended to use sourceTensor.clone().detach() or sourceTensor.clone().detach().requires_grad_(True), rather than torch.tensor(sourceTensor).
  p2c_att = torch.matmul(key_layer, torch.tensor(pos_query_layer.transpose(-1, -2), dtype=key_layer.dtype))
```
This PR fixes the warnings by using .to(dtype=)  rather than tensor(...,dtype=)



_The documentation is not available anymore as the PR was closed or merged._<|||||>@LysandreJik any thoughts?