Incorrect updated affine in `NrrdReader`

[KumoLiu]

• The docstring for reverse_indexing in ITKReader is wrong.
  

  MONAI/monai/data/image_reader.py

  Lines 170 to 173 in abe2e31

  	reverse_indexing: whether to use a reversed spatial indexing convention for the returned data array.
  	If ``False``, the spatial indexing follows the numpy convention;
  	otherwise, the spatial indexing convention is reversed to be compatible with ITK. Default is ``False``.
  	This option does not affect the metadata.

  
  

  MONAI/monai/data/image_reader.py

  Lines 368 to 372 in abe2e31

  	np_img = itk.array_view_from_image(img, keep_axes=False)
  	if img.GetNumberOfComponentsPerPixel() == 1: # handling spatial images
  	return np_img if self.reverse_indexing else np_img.T
  	# handling multi-channel images
  	return np_img if self.reverse_indexing else np.moveaxis(np_img.T, 0, -1)

  
  https://github.com/InsightSoftwareConsortium/ITK/blob/f5aab1f68e53061264f4f6f3af5e0d49c5f7481d/Wrapping/Generators/Python/itk/support/extras.py#L351-L354

• In NrrdReader, even the header have been updated after _convert_f_to_c_order, it dosen't pass to the _get_affine, so the affine is still not updated.
  

  MONAI/monai/data/image_reader.py

  Lines 1324 to 1326 in abe2e31

  	if self.index_order == "C":
  	header = self._convert_f_to_c_order(header)
  	header[MetaKeys.ORIGINAL_AFFINE] = self._get_affine(i)