Hide out of stock related pages

function kt_hide_out_of_stock_option( $option ){
    return 'yes';
}

add_action( 'woocommerce_before_template_part', function( $template_name ) {

    if( $template_name !== "single-product/related.php" ) {
        return;
    }

    add_filter( 'pre_option_woocommerce_hide_out_of_stock_items', 'kt_hide_out_of_stock_option' );

} );

add_action( 'woocommerce_after_template_part', function( $template_name ) {

    if( $template_name !== "single-product/related.php" ) {
        return;
    }

    remove_filter( 'pre_option_woocommerce_hide_out_of_stock_items', 'kt_hide_out_of_stock_option' );

} );