LAION Open Assistant data is already released

[johnnynoone]

README.md says:

Consider supporting the LAION Open Assistant effort to produce a high-quality dataset for supervised fine-tuning (or bugging them to release their data).

But the Open Assistant project is over and the data is already released (see the OA webpage for info). From what I understand, this is their final dataset: https://huggingface.co/datasets/OpenAssistant/oasst2 . So it's time to make use of that data and remove this part from the README.