conformer export problems 
**Describe the bug**
Trying to export conformer to TorchScript, using `model.export('conformer.pt')` and [/scripts/export.py](https://github.com/NVIDIA/NeMo/blob/main/scripts/export.py). Getting error:
`RuntimeError: Type 'Tuple[Tensor, Tensor, NoneType, NoneType]' cannot be traced. Only Tensors and (possibly nested) Lists, Dicts, and Tuples of Tensors can be traced`

This is true for conformer trained on the Nemo version 1.12.
But everything is ok with exporting old version of conformer (trained on Nemo 1.10) and with that Nemo version installed.
