[Bug] A bug in filtering checkpoints
**Describe the bug**

https://github.com/NVIDIA/NeMo/blob/cfbe0924db02a1a557aeeea55cc1a01b83903e71/nemo/utils/callbacks/nemo_model_checkpoint.py#L98-L99

I think Line 99 should be
```python
 if index != len(self.monitor): 
```