Update autoencoder_kl_cosmos.py

[tanuj-rai]

What does this PR do?

This PR replaces an incorrect call to torch.reshape(...) with hidden_states.reshape(...) to prevent NameError.

Fixes #12025

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Who can review?

@a-r-r-o-w

[a-r-r-o-w]

Thanks!

[HuggingFaceDocBuilderDev]

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[a-r-r-o-w]

@tanuj-rai Could you run make style and push the changes?

[a-r-r-o-w]

@bot /style

[github-actions]

Style bot fixed some files and pushed the changes.

[tanuj-rai]

@tanuj-rai Could you run make style and push the changes?

I am really Sorry @a-r-r-o-w, I have missed your comment, but thank you for merging the PR.

[a-r-r-o-w]

No worries, I forgot we had a bot setup to help with style fixes :)