Add docs xlm roberta
# What does this PR do?

Fixes  [20055](https://github.com/huggingface/transformers/issues/20055)

I have opened a fresh PR to add resources for XLM-RoBERTa. 
1. Added a link to classification task  fine-tuning using Habana Gaudi blog 
2. Fix typos
3. Remove TF and Flax XLMRobertaForCausalLM 
4. Update my branch to reflect the latest main branch

Thanks for your help reviewing the changes! @stevhliu 
_The documentation is not available anymore as the PR was closed or merged._