Change audio kwarg to images in TROCR processor
# What does this PR do?

Fix a bug in TROCR processor introduced in #18325

Currently, we have [failed job run](https://github.com/huggingface/transformers/runs/7603716998?check_suite_focus=true) with error

```bash
        if audio is None and text is None:
>           raise ValueError("You need to specify either an `audio` or `text` input to process.")
E           ValueError: You need to specify either an `audio` or `text` input to process.
```
_The documentation is not available anymore as the PR was closed or merged._