Dashboard 2.0 ui-chart - Don't show the Legend

I need to place some lines and other information on a chart that doesn't require a legend to be displayed. For example, these upper and lower limits are two lines. But the legend must be for other lines.


Here I would like to remove the "min" and "max" labels Legend, but leave their lines, and leave the label Voltage.
I tried passing different parameters to msg.ui_update.chartOptions but it doesn't work. Is it possible to do this or not?