Update `ZeroShotObjectDetectionPipeline` doc example (#20528)
* Update ZeroShotObjectDetectionPipeline expect output
* Update src/transformers/pipelines/zero_shot_object_detection.py
Co-authored-by: Nicolas Patry <patry.nicolas@protonmail.com>
Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>
Co-authored-by: Nicolas Patry <patry.nicolas@protonmail.com>