How do we remove edits from a picture, specific to remove a black bar which was added on top via MS Paint?
As you said, it's a JPEG file. You can only remove a black part if the file has layers: whatever is underneath the black part needs to be stored in the file as well. For JPEG files that's not the case: the black part has simply replaced the previous content so it's no longer part of the file. So it's not possible in this situation.