Move rescale dtype recasting to match torchvision ToTensor (#25229)

Move dtype recasting to match torchvision ToTensor

Author: amyeroberts

src/transformers/image_transforms.py

@@ -110,11 +110,12 @@ def rescale(
     if not isinstance(image, np.ndarray):
         raise ValueError(f"Input image must be of type np.ndarray, got {type(image)}")
 
-    image = image.astype(dtype)
-
     rescaled_image = image * scale
     if data_format is not None:
         rescaled_image = to_channel_dimension_format(rescaled_image, data_format)
+
+    rescaled_image = rescaled_image.astype(dtype)
+
     return rescaled_image