test: add test CT_GrpObFrm.new_cht_graphicFrame()
test: add test CT_GrpObFrm.new_cht_graphicFrame()

biggihs/python-pptx,cchanrhiza/python-pptx,scanny/python-pptx,AlexMooney/python-pptx,kevingu1003/python-pptx,hoopes/python-pptx