COMP: Fix SlicerWizard/Utilities.py for Python 2.6

Use tuples instead of set literals for checking for a supported VCS
tool, as set literals are only supported in Python 2.7.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23219 3bd1e089-480b-0410-8dfb-8563597acbee