Failing slow AutoModelTest/BertForPreTraining
```
RUN_SLOW=1 pytest tests/test_modeling_auto.py::AutoModelTest::test_model_for_pretraining_from_pretrained
```
Have not investigated at all, but wanted to record since the slow test failures are evasive :)


Clues:
model: `transformers.modeling_bert.BertForPreTraining`
```
loading_info = {'missing_keys': ['cls.predictions.decoder.bias'], 'unexpected_keys': [], 'error_msgs': []}
```
Likely related to this funkiness

https://github.com/huggingface/transformers/blob/ee5de0ba449d638da704e1c03ffcc20a930f5589/src/transformers/modeling_bert.py#L482-L483
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