Added type hints for TF: rag model
Based on Issue https://github.com/huggingface/transformers/issues/16059

Type hints for the [TFRagModel](https://huggingface.co/docs/transformers/model_doc/rag) have been added.

@Rocketknight1 Could you please check the changes and merge if it's fine?

Thanks a lot.
_The documentation is not available anymore as the PR was closed or merged._<|||||>@Rocketknight1 can you take a look at this? I just added type hints and fixed a syntax error in one previous type. Still it shows it failed these 2 tests. I have no idea what these tests do, can you shed some light on this issue?<|||||>Thanks a lot @Rocketknight1, I have made the suggested changes!<|||||>Looks perfect now, thank you!