Fix variable name in docstring for PeftAdapterMixin.set_adapters

[geekuillaume]

What does this PR do?

Fix docstring for PeftAdapterMixin.set_adapters. It was previously indicating that the second argument is adapter_weights when it actually is weights.

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Who can review?

@sayakpaul who initially pushed this code here https://github.com/huggingface/diffusers/pull/8981/files#diff-fdc2e14a8c1091d917cf31ca155be9baa8095d704bd2a2f58970ec31641c0cae

[sayakpaul]

Thanks!

[HuggingFaceDocBuilderDev]

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