Remove 2 failing ONNX conversion tests
# What does this PR do?

After ##22212, two tests start to fail.
OK. But should we do something like removing CI regarding this? Currently failing tests pop up.<|||||>_The documentation is not available anymore as the PR was closed or merged._<|||||>I think you can remove the tests as well.<|||||>@sgugger Just to confirm, we want/could remove all things like 

- `ConvertCommand` in `src/transformers/commands/transformers_cli.py`
- `export_with_transformers` in `src/transformers/onnx/__main__.py`
- the file `src/transformers/onnx/convert.py` and any test using this fle

also cc @michaelbenayoun @fxmarty <|||||>No we're not removing code, just the tests if they start failing.<|||||>OK, glad I ask!<|||||>Ping @sgugger again to draw a bit of his attention.