There are several options to optimize your traced output. A small movable window should be called Tracing Settings that has an option to remove double lines although as I test your image that option does not fix what you are trying to fix.
There is a drop down at the top left of the user interface that defaults to "Auto Colors"; change this to Centerline and play with the Mask settings in the Tracing Setting floating window and you will get a good trace of your image (as I am able to).