Revert "Remove absent helper method"

This reverts commit dee87fe.

Author: toddbc

app/code/Meta/Conversion/Test/Unit/Observer/AddToCartTest.php

@@ -90,6 +90,7 @@ public function testAddToCartEventCreated()
         $product->setName('Earphones');
         $this->request->method('getParam')->willReturn($sku);
         $this->magentoDataHelper->method('getProductBySku')->willReturn($product);
+        $this->magentoDataHelper->method('getProductById')->willReturn($product);
 
         $observer = new Observer(['eventId' => $eventId]);