Notebook bugfixes
Fixes notebook bugs for r1.5.0 release:

Bug 3415701
https://nvbugswb.nvidia.com/NVBugs5/redir.aspx?url=/3415701 [ML-NeMo][Tesla A30][NLP] Zero_Shot_Intent_Recognition.ipynb failed with FileNotFoundError: [Errno 2] No such file or directory:


Bug 3415458
https://nvbugswb.nvidia.com/NVBugs5/redir.aspx?url=/3415458 [ML-NeMo][Tesla A30][NLP] Relation_Extraction-BioMegatron.ipynb failed with ValueError: megatron-lm BERT models have been deprecated in NeMo 1.5+


Bug 3415486
https://nvbugswb.nvidia.com/NVBugs5/redir.aspx?url=/3415486 [ML-NeMo][Tesla A30][NLP] Token_Classification-BioMegatron.ipynb failed with ValueError: megatron-lm BERT models have been deprecated in NeMo 1.5+


Bug 3415335
https://nvbugswb.nvidia.com/NVBugs5/redir.aspx?url=/3415335 [ML-NeMo][Tesla A30][NLP] Entity_Linking_Medical.ipynb failed with MisconfigurationException: You have asked for `amp_level='O1'` which is not supported with `amp_backend='native'`.