Rag end2end new
# What does this PR do?

I revamped the **[rag-end2end-retriever](https://github.com/huggingface/transformers/tree/main/examples/research_projects/rag-end2end-retriever)** to be compatible with the latest versions of PL and RAY. This was requested by @aaronmueller. 

@patrickvonplaten  
_The documentation is not available anymore as the PR was closed or merged._<|||||>> Ok for me! Could we maybe though delete the commented out code?

Thanks a lot for the update. I did remove unwanted comments. Please let me know if I need to do anything more.