Removing underlone from navigation

Site URL: https://www.christopherhorwood.com/

Hello,

I'm using  7.1 and would like to remove the underline on the active navigation link.  Any ideas?

https://www.christopherhorwood.com/

I' ve tried the code

.header-nav-item--active a {
   background-image: none;
}

but no luck

Thanks

Add to Home > Design > custom CSS

.header-nav-item--active a {
    background-image: none !important;
}