Question about saving peft checkpoint

### 🐛 Describe the bug

From my understand, when saving checkpoints for peft models (see [here](https://github.com/CarperAI/trlx/blob/bcd237f1e94c84c5c9f5a4086bab34c0946e3fa7/trlx/trainer/accelerate_base_trainer.py#L315)), trlx removes `pytorch_model.bin` before calling `save_pretrained` which makes the removal useless in my opinion.

Is this intentional or we should move the removal code after `save_pretrained` is called?

Here is an example of a directory resulting from `save_pretrained`:
```
adapter_config.json adapter_model.bin optimizer.bin pytorch_model.bin random_states_0.pkl special_tokens_map.json spiece.model tokenizer_config.json tokenizer.json
```

### Which trlX version are you using?

0.7.0

### Additional system and package information

3.10.12

Start in trlx/trainer/accelerate_base_trainer.py around line 315 and trace the checkpoint-saving order for PEFT models. Reproduce the save_pretrained output with trlX 0.7.0, then verify whether pytorch_model.bin is removed at the intended point and whether the resulting checkpoint contents match the expected behavior.

Written by the indexing model from the issue text.