Update ChangeTrackerPy

BUG: account for the changes in CTK API that caused the self-test and the module
functionality to break

The CTK commit to blame: https://github.com/commontk/CTK/commit/9aa389d2bfbd816b41229b517451912d891bc968#Libs/Widgets/ctkWorkflowButtonBoxWidget.h

Details:
https://github.com/fedorov/ChangeTrackerPy/compare/47aca45...9177bbe