Update ControlNet Inpaint single file test

[DN6]

What does this PR do?

#6975 makes it so that the StableDiffusionControlNetInpaintPipeline defaults to using 9 channels for the UNet config.

This PR updates the StableDiffusionControlNetInpaintPipeline test to use the 9 channel UNet checkpoint when running the from_single_file test.

Fixes # (issue)

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[HuggingFaceDocBuilderDev]

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[sayakpaul]

Thanks!