`DocumentQuestionAnsweringPipeline` only for fast ⚡ tokenizers
# What does this PR do?

So let's make this more clear and explicit.
_The documentation is not available anymore as the PR was closed or merged._<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_22745). All of your documentation changes will be reflected on that endpoint.