Remove looped item save

CartItemRepositoryInterface::save trigger quote collection and save. The update
cart items resolver accepts multiple quote items and save the quote. Saving
each quote item increases the quote save by the number of items passed in the
update request.

Author: pmclain

app/code/Magento/QuoteGraphQl/Model/Cart/UpdateCartItem.php

@@ -117,7 +117,6 @@ private function updateItemQuantity(int $itemId, Quote $cart, float $quantity)
         }
         $cartItem->setQty($quantity);
         $this->validateCartItem($cartItem);
-        $this->cartItemRepository->save($cartItem);
     }
 
     /**