/**
* @snippet       Remove Sorting Option @ WooCommerce Shop
* @how-to        Get CustomizeWoo.com FREE
* @author        Rodolfo Melogli
* @testedwith    WooCommerce 3.8
* @donate $9     https://businessbloomer.com/bloomer-armada/
*/
  
add_filter( 'woocommerce_catalog_orderby', 'bbloomer_remove_sorting_option_woocommerce_shop' );
  
function bbloomer_remove_sorting_option_woocommerce_shop( $options ) {
   unset( $options['rating'] );   
   return $options;
}
  
// Note: you can unset other sorting options by adding more "unset" calls... here's the list: 'menu_order', 'popularity', 'rating', 'date', 'price', 'price-desc'