Fix oneformer instance segmentation RuntimeError

[yhshin11]

What does this PR do?

Fixes RuntimeError when running on GPU due to inconsistent devices in OneFormerImageProcessor.

Same issue was fixed in image_processing_mask2former.py but not in image_processing_oneformer.py

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[ArthurZucker]

Thanks!

[HuggingFaceDocBuilderDev]

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