add_filter( 'unicase_footer_social_icons_args', 'uc_child_remove_rss', 100 );

function uc_child_remove_rss( $args ) {
    foreach ( $args as $key => $arg ) {
        if ( $arg['id'] == 'rss' ) {
            unset( $args[$key] );
        }
    }
    return $args;
}