Docker: add `speech` dep to the consistency docker image
Author: gante
Pull request: yes

# What does this PR do?

See title :)

### Why is this being added?
1. I'm working on adding more repository checks
2. A missing check is whether methods we explicitly request to document in the `*.mdx` files have a docstring (we have this check for the documented classes, but not for the documented methods).
3. This check requires inspecting objects
4. Inspecting an object requires loading it, realizing the lazy imports

I've opened a preliminary PR with this check [here](https://github.com/huggingface/transformers/pull/32320), but [CI complaining about missing audio dependencies](https://app.circleci.com/pipelines/github/huggingface/transformers/99261/workflows/a82b7613-4563-4011-9667-f73a02fd881f/jobs/1319765).

My plan is to:
1. Merge this extra dependency
2. Wait a day for the new CI images to be built
3. Reopen https://github.com/huggingface/transformers/pull/32320, which adds the check described above.
4. After this check is merged, work on a check over the contents of the explicitly documented methods (`check_docstring.py` currently only checks/fixes non-empty class docstrings) 👉 better quality docs with no manual work

Comments:
For my own understanding, regarding this step: 

`Inspecting an object requires loading it, realizing the lazy imports`

Is this because of needing to have access to object methods? We should be able to import without dependencies being installed 

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_32374). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

> Are the steps for `build ci image` only applicable for model tests?

@amyeroberts If by `build ci image` you are referring to the guide we have on Notion to manually update our CI image, then it applies to all CI jobs including this one.

The options for CI jobs that need updated images are:
- Follow the guide on notion, have the image ready in a hour or two (manual steps)
- Push changes, wait for the daily job (automated) 👈  going with this one, given that the task is not urgent and it takes less time/energy from me

As we've chatted before, we should improve this process :)

@amyeroberts oops, forgot to answer this one before deciding whether to merge!

> Is this because of needing to have access to object methods? We should be able to import without dependencies being installed

More specifically, the line that makes the import required is `if not hasattr(obj_class, method):` (see stack trace [here](https://app.circleci.com/pipelines/github/huggingface/transformers/99261/workflows/a82b7613-4563-4011-9667-f73a02fd881f/jobs/1319765))

Is there an import-less way to access the methods of an instance? Could we be missing some gating?


> @amyeroberts oops, forgot to answer this one before deciding whether to merge!

No worries, I was happy for you to merge, I just wanted to understand the issue better : )

> Is there an import-less way to access the methods of an instance? Could we be missing some gating?

We could create the methods in our dummy objects, but at the moment I don't think so

> > Are the steps for `build ci image` only applicable for model tests?
> 
> @amyeroberts If by `build ci image` you are referring to the guide we have on Notion to manually update our CI image, then it applies to all CI jobs including this one.
> 
> The options for CI jobs that need updated images are:
> 
> * Follow the guide on notion, have the image ready in a hour or two (manual steps)
> * Push changes, wait for the daily job (automated) 👈  going with this one, given that the task is not urgent and it takes less time/energy from me
> 
> As we've chatted before, we should improve this process :)

Thanks for clarifying - I didn't realise there were two ways!