deepspeed typing Dict error
### System Info

- `transformers` version: 4.32.0.dev0
- Platform: Linux-5.10.179-171.711.amzn2.x86_64-x86_64-with-glibc2.26
- Python version: 3.9.16
- Huggingface_hub version: 0.15.1
- Safetensors version: 0.3.1
- Accelerate version: 0.22.0.dev0
- Accelerate config:    not found
- PyTorch version (GPU?): 2.0.1+cu118 (True)
- Tensorflow version (GPU?): not installed (NA)
- Flax version (CPU?/GPU?/TPU?): not installed (NA)
- Jax version: not installed
- JaxLib version: not installed
- Using GPU in script?: <fill in>
- Using distributed or parallel set-up in script?: <fill in>

### Who can help?

@sgugger 

### Information

- [X] The official example scripts
- [ ] My own modified scripts

### Tasks

- [X] An officially supported task in the `examples` folder (such as GLUE/SQuAD, ...)
- [ ] My own task or dataset (give details below)

### Reproduction

Right now any command with `--deepspeed /path/to/json` will fail and throw the following error
```
--deepspeed: invalid Dict value
```
This is reported in https://github.com/huggingface/transformers/pull/24549#issuecomment-1613046347 but the merged fix https://github.com/huggingface/transformers/pull/24574 does not resolve this.
In fact the `deepspeed: Union[str, Dict]` field in `training_args.py` still raise the error when the `deepspeed` is passed as the string. This seems to be a limitation of python dataclass.

### Expected behavior

`deepspeed` flag should support string.
Yes, this has been broken by #24550 again...