Fix transformer shape type dropdown bug

Summary:
The shape drop down would reset whenever a transformer
question was saved, because the select value= was set
incorrectly. This commit makes it set via props.shape.type
instead of the no-longer-existant props.type

Test Plan:
Edit test.html to be a polygon-4 instead of a polygon-3;
test that when loading test.html the shape type dropdown
says "Quadrilateral" instead of "Triangle"