Fix ProphetNetTokenizer
# What does this PR do?


Fix `ProphetNetTokenizer`: `ProphetNet` doesn't have `token_type_ids` as argument.

Without this PR, the docstring examples will give the following errors:

```
in _call_impl
                return forward_call(*input, **kwargs)
            TypeError: forward() got an unexpected keyword argument 'token_type_ids'
```
_The documentation is not available anymore as the PR was closed or merged._