Fixes path for Graphormer checkpoint
# What does this PR do?

@ydshieh - should fix the graphormer checkpoint path problem.

## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).

## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.
_The documentation is not available anymore as the PR was closed or merged._<|||||>@clefourrier We now get some other issues, see the [failed job run](https://github.com/huggingface/transformers/actions/runs/4060331156/jobs/6989383705)

Could you take a look 🙏? Don't hesitate if you need some help. 

Error message provided here
```bash
FAILED tests/models/graphormer/test_modeling_graphormer.py::GraphormerModelTest::test_model_from_pretrained - RuntimeError: Error(s) in loading state_dict for GraphormerForGraphClassification:
	size mismatch for classifier.classifier.weight: copying a param with shape torch.Size([1, 768]) from checkpoint, the shape in current model is torch.Size([2, 768]).
	You may consider adding `ignore_mismatched_sizes=True` in the model `from_pretrained` method.
FAILED tests/models/graphormer/test_modeling_graphormer.py::GraphormerModelIntegrationTest::test_inference_graph_classification - RuntimeError: Error(s) in loading state_dict for GraphormerForGraphClassification:
	size mismatch for classifier.classifier.weight: copying a param with shape torch.Size([1, 768]) from checkpoint, the shape in current model is torch.Size([2, 768]).
	You may consider adding `ignore_mismatched_sizes=True` in the model `from_pretrained` method.
```

<|||||>@ydshieh Opened PR #21419 to fix this!