Typo in curator_merging.py and curator_sorting.py

[gauharbains]

There is a typo in the following files : curator_sorting.py and curator_merging.py. I came across this while working on integrating the iterative deep learning segmentation workflow into our platform that we are deploying for the NIH.

Link to the branch containing the fix : https://github.com/gauharbains/aics-ml-segmentation/tree/fix_typo