[`Blip`] Fix blip output name
As suggested by @ydshieh offline and similarly as https://github.com/huggingface/transformers/pull/22893
In fact, there is no reason to call the output logits `decoder_logits`, as they always come from the decoder

cc @sgugger @ydshieh 

_The documentation is not available anymore as the PR was closed or merged._<|||||>Hi thanks for this @younesbelkada ❤️ 

However, this is not enough, you have to add something like 

https://github.com/huggingface/transformers/blob/3ec10e6c76362191b61260300fe1d6173a8dd7e1/src/transformers/models/swin/modeling_swin.py#L171-L177

in that PR to make backward compatibility.

(unless @sgugger say this model is still recent and/or not high usage)<|||||>Thanks @ydshieh for double checking, I missed that, it should be now added! :D <|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_24889). All of your documentation changes will be reflected on that endpoint.