Only Show 2 Category in Single Post

/* Only Show 2 Category in Single Post */
function show_only_2_category( $thelist ) {
    if ( is_single() && is_singular() ) {
        $thelist = array( $thelist[0], $thelist[1] ); /* Set Only First 2 Category */
        return $thelist;
    }

    return $thelist;
}
add_filter( 'the_category_list', 'show_only_2_category', 999 );