How can I change a tab widget content's margin?

Using the Tabs widget in ThingWorx 8.5.7, it adds a 20px margin around the content of each tab.  Is there a way to remove or reduce that margin?

I found another topic here about adjusting the margin in a Tabs widget with a solution of the custom CSS below, but adding that CSS doesn't change anything for me.

ptcs-page-select::part(pages)

{

margin: 10px !important;

}