Fix compatibility causallm models export with optimum 1.15

[eaidova]

Fix export CausalLM models with new optimum version applying workaround from #477 only for 1.14

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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[HuggingFaceDocBuilderDev]

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[echarlaix]

Thanks for the fix @eaidova !

[echarlaix]

To fix the quality test, please run the make style command

[eaidova]

To fix the quality test, please run the make style command

thanks, applied