Update Code example according to deprecation of AutoModeWithLMHead
Author: savigny030
Pull request: yes
Labels: name: model card

'The class `AutoModelWithLMHead` is deprecated and will be removed in a future version. Please use `AutoModelForCausalLM` for causal language models, `AutoModelForMaskedLM` for masked language models and `AutoModelForSeq2SeqLM` for encoder-decoder models.'
I dont know how to change the 'How to use this model directly from the 🤗/transformers library:' part since it is not part of the model-paper

# What does this PR do?

Fix the future deprecation of `AutoModelWithLMHead`

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Comments:
@julien-c what is the test that failed testing? i mean, there is no test that should fail because of my minor changes...