[dreambooth] link to bitsandbytes readme for installation (#1229)

* add 'conda install cudatoolkit' to dreambooth 'training on 16GB' example 

fixes https://github.com/huggingface/diffusers/issues/1207



* Apply suggestions from code review
Co-authored-by: Suraj Patil <surajp815@gmail.com>

examples/dreambooth/README.md

@@ -92,7 +92,7 @@ accelerate launch train_dreambooth.py \
 
 With the help of gradient checkpointing and the 8-bit optimizer from bitsandbytes it's possible to run train dreambooth on a 16GB GPU.
 
-Install `bitsandbytes` with `pip install bitsandbytes`
+To install `bitandbytes` please refer to this [readme](https://github.com/TimDettmers/bitsandbytes#requirements--installation).
 
 ```bash
 export MODEL_NAME="CompVis/stable-diffusion-v1-4"