Update plantcv/plantcv/median_blur.py
Update plantcv/plantcv/median_blur.py

Co-Authored-By: HaleySchuhl <8ba9e1811e40b6437e8d5f550320a48cf601d1bc@gmail.com>
danforthcenter/plantcv,danforthcenter/plantcv,danforthcenter/plantcv,stiphyMT/plantcv,stiphyMT/plantcv,stiphyMT/plantcv