Hide out of stock products in woocommerce related products

functions.php

<?php

class WPDeskHideOutOfStockInRelated {

	public function hooks() {
		add_action( 'woocommerce_after_single_product_summary', array( $this, 'add_filter' ), 19 );
		add_action( 'woocommerce_after_single_product_summary', array( $this, 'remove_filter' ), 21 );
	}

	public function add_filter() {
		add_filter( 'option_woocommerce_hide_out_of_stock_items', array( $this, 'return_yes' )  );
	}

	public function remove_filter() {
		remove_filter( 'option_woocommerce_hide_out_of_stock_items', array( $this, 'return_yes' )  );
	}

	public function return_yes() {
		return 'yes';
	}

}
(new WPDeskHideOutOfStockInRelated())->hooks();