[Bugfix] Fix KeyError on loading GPT-NeoX

[jsato8094]

This small PR, like #1978, solves the problem of loading GPT-NeoX model parameters into the vLLM, which causes a KeyError due to the presence of rotary_emb.cos_cached and rotary_emb.sin_cached.
We noticed this problem when we loaded GPT-NeoX model fine-tuned with OpenRLHF.
This implementation is the same as in other models such as Llama.

FIX #xxxx (link existing issues this PR will resolve)

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[WoosukKwon]

@jsato8094 LGTM. thanks for adding the comment.