Installing your own theme-component and attaching it to the theme should work. You will want to add this line into the css of the theme component.
.custom-category-boxes .description {
display: none;
}
To install a custom theme component you will go to /admin/customize/themes click Install then click Create New.
From there you will be taken to the new component’s page, where you will select which theme you want it to be included on.
You can then click Edit CSS + Html and add the code I sent you above to the common.scss file.