Drop `feature_extractor_type` when loading an image processor file (#28195)

fix
Co-authored-by: ydshieh <ydshieh@users.noreply.github.com>

src/transformers/image_processing_utils.py

@@ -75,6 +75,9 @@ class ImageProcessingMixin(PushToHubMixin):
 
     def __init__(self, **kwargs):
         """Set elements of `kwargs` as attributes."""
+        # This key was saved while we still used `XXXFeatureExtractor` for image processing. Now we use
+        # `XXXImageProcessor`, this attribute and its value are misleading.
+        kwargs.pop("feature_extractor_type", None)
         # Pop "processor_class" as it should be saved as private attribute
         self._processor_class = kwargs.pop("processor_class", None)
         # Additional attributes without default values