[Refactor] How attention is set in 3D UNet blocks

[DN6]

What does this PR do?

There's some confusion around how num_attention_heads is being used in the 3D UNet + Block. This PR attempts to fix the issue by correcting the values used for num_attention_heads

Related: https://github.com/huggingface/diffusers/pull/6872 https://github.com/huggingface/diffusers/pull/6873

Fixes # (issue)

Before submitting

• [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• [ ] Did you write any new necessary tests?

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[HuggingFaceDocBuilderDev]

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[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

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[yiyixuxu]

@DN6 let's finish up this soon:)

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the contributing guidelines are likely to be ignored.

[DN6]

@yiyixuxu Anything specific you wanted to address in this current PR?

[DN6]

Oh wait. Nvm I haven't addressed those initial comments. Will wrap this up.

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the contributing guidelines are likely to be ignored.