Skip a failing test on main for now
# What does this PR do?

On CircleCI, we have a failure on `main`:
```
FAILED tests/models/roberta/test_modeling_roberta.py::RobertaModelTest::test_assisted_greedy_search_matches_greedy_search
```

(BTW, it works on daily CI GPU runners)
_The documentation is not available anymore as the PR was closed or merged._<|||||>Merge as it just skip the failing test.