Fix batching tests for new models (Mamba and SegGPT) (#29633)
* fix batchinng tests for new models
* Update tests/models/seggpt/test_modeling_seggpt.py
Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>
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Co-authored-by: amyeroberts <22614925+amyeroberts@users.noreply.github.com>