Add CV + audio labels to glossary
This is a [follow-up PR ](https://github.com/huggingface/transformers/pull/20051#discussion_r1013978694) to expand the `labels` definition to include expected labels for model heads from other modalities.
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_20114). All of your documentation changes will be reflected on that endpoint.