Remove woo_discount_rules menu for shop_manager user role

Remove the woo_discount_rules menu for the shop_manager user role.

function wdr_remove_woocommerce_submenu() {

    $user = wp_get_current_user();
    if ( isset( $user['roles'][0] ) && $user['roles'][0] == 'shop_manager' ) {
        remove_submenu_page( 'woocommerce', 'woo_discount_rules' );    // when user is shop manager
    } 
}

add_action( 'admin_menu', 'wdr_remove_woocommerce_submenu', 99, 0 );