DEISMultistepScheduler not working on FLUX

### Describe the bug

DEISMultistepScheduler not working on FLUX

### Reproduction

import torch
from diffusers import FluxPipeline
from diffusers.schedulers import DEISMultistepScheduler

pipe = FluxPipeline.from_pretrained("black-forest-labs/FLUX.1-dev", torch_dtype=torch.bfloat16)
pipe.scheduler = DEISMultistepScheduler.from_config(pipe.scheduler.config, timestep_spacing="linspace")

prompt = "A cat holding a sign that says hello world"
image = pipe(
prompt,
height=1024,
width=1024,
guidance_scale=3.5,
num_inference_steps=50,
max_sequence_length=512,
generator=torch.Generator("cpu").manual_seed(0)
).images[0]
image.save("flux-dev.png")

### Logs

```shell
ValueError: The current scheduler class 's `set_timesteps` does not support custom sigmas schedules. Please check whether you are using the correct scheduler.
```

### System Info

- 🤗 Diffusers version: 0.31.0
- Platform: Linux-5.10.0-28-amd64-x86_64-with-glibc2.31
- Running on Google Colab?: No
- Python version: 3.10.14
- PyTorch version (GPU?): 2.4.0+cu121 (True)
- Flax version (CPU?/GPU?/TPU?): not installed (NA)
- Jax version: not installed
- JaxLib version: not installed
- Huggingface_hub version: 0.24.6
- Transformers version: 4.45.1
- Accelerate version: 0.34.0
- PEFT version: 0.12.0
- Bitsandbytes version: 0.43.3
- Safetensors version: 0.4.4
- xFormers version: not installed
- Accelerator: NVIDIA A100-SXM4-80GB, 81920 MiB
NVIDIA A100-SXM4-80GB, 81920 MiB
- Using GPU in script?:
- Using distributed or parallel set-up in script?:

### Who can help?

_No response_

Start at diffusers/schedulers/scheduling_deis_multistep.py, especially set_timesteps, and compare its handling of the FLUX scheduler configuration with the supplied FluxPipeline reproduction. Run the example on the stated versions; done means DEISMultistepScheduler can be assigned to FluxPipeline and inference completes without the custom-sigmas ValueError.

Vom Indexierungsmodell aus dem Issue-Text verfasst.