Remove invalid coupon error message

Eliminate the error message for invalid coupons.

add_filter( 'woocommerce_coupon_error', function($err, $err_code, $coupon){
        if(is_object($coupon) && method_exists($coupon, 'get_code')){
    		if( in_array($coupon->get_code(), array('black friday', 'cyber monday'))){
			$err  =  ''; 
		}
    	}
	return $err;
}, 30, 3 );