Fix docs link to train_unconditional.py (#642)

the link points to an old location of the train_unconditional.py file

Author: AbdullahAlfaraj

examples/README.md

@@ -38,7 +38,7 @@ Training examples show how to pretrain or fine-tune diffusion models for a varie
 
 | Task | 🤗 Accelerate | 🤗 Datasets | Colab
 |---|---|:---:|:---:|
-| [**Unconditional Image Generation**](https://github.com/huggingface/transformers/tree/main/examples/training/train_unconditional.py) | ✅ | ✅ | [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/huggingface/notebooks/blob/main/diffusers/training_example.ipynb)
+| [**Unconditional Image Generation**](https://github.com/huggingface/diffusers/blob/main/examples/unconditional_image_generation/train_unconditional.py) | ✅ | ✅ | [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/huggingface/notebooks/blob/main/diffusers/training_example.ipynb)
 
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