[Whisper] Remove embed_tokens from encoder docstring
Author: sanchit-gandhi
Pull request: yes

# What does this PR do?

`embed_tokens` is not an arg for the `WhisperEncoder`. It looks like it was copied from BART (where we do use it) and left in by mistake!
https://github.com/huggingface/transformers/blob/9402788b34fbc6581ae9d7d9d68612a96d9aa111/src/transformers/models/bart/modeling_bart.py#L708

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Comments:
_The documentation is not available anymore as the PR was closed or merged._

Rebased and pushed two dummy commits to re-trigger the CI after GH SSO (no new changes to the PR in the last two commits https://github.com/huggingface/transformers/pull/21996/commits/ef692e28e650d305ba2947c21b572b447d0eb01f and https://github.com/huggingface/transformers/pull/21996/commits/ecfddec7b2ff4958e3fe3259d09ed5e681cf8fe1)

@sanchit-gandhi 

For trigger CI, you can do sth like `git commit --allow-empty -m "Empty commit to trigger CI"`
(in the future when you need it)

Thanks for the tip @ydshieh! Looks the CI is red on main due to a `500 Server Error` with the HF Hub, see https://github.com/huggingface/transformers/actions/runs/4392426382/jobs/7692183097.

I re-run that CI job and it is green now :-)

The failed test in the job `test_tf` is irrelevant to this PR I believe.

Amazing, thanks @ydshieh! 🙌