remove `return_dict_in_generate` condition on storing scores.
# What does this PR do?
Fixes an issue in `generate` where the `output_scores` (or `output_attentions` or `output_hidden_states` ) cannot be obtained unless `return_dict_in_generate`  is set to `True`. This is problematic because it's not what we want when we have a flag for each of these outputs. 
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_19373). All of your documentation changes will be reflected on that endpoint.