Comet: Undocumented and incorrectly described function

Nobody has claimed this yet.

The Comet function `log_model` has no formal documentation and what little is written is _wrong_. None of the Comet examples include this function.

See [logger.experiment.log_model(name="my-model", "path to your model")](https://github.com/Lightning-AI/pytorch-lightning/blob/ea59e403367871a782becc5c327d7bafbd43bf8c/src/lightning/pytorch/loggers/comet.py#L163)

## The correct function definition:
```Python
logger.experiment.log_model(name="my-model", file_or_folder="")
```

## A working example
Assuming Trainer `enable_checkpointing` is `True`:
```Python
class DNN(pl.LightningModule):
def __init__(self):
...
on_train_end(self):
self.logger.experiment.log_model(
name="",
file_or_folder=self.trainer.checkpoint_callback.last_model_path,
)
```

cc @lantiga @borda

Start with src/lightning/pytorch/loggers/comet.py at the log_model entry point referenced in the issue, then locate the related documentation and examples. Update the description and examples to use file_or_folder and the checkpoint path shown; done means the function is formally documented and no longer described incorrectly.

Written by the indexing model from the issue text.