fix: calculate stock_value_diff

`d.item_tax_amount` is already in base currency.

(cherry picked from commit 5df5851798)

erpnext/stock/doctype/purchase_receipt/purchase_receipt.py

@@ -572,9 +572,7 @@ class PurchaseReceipt(BuyingController):
 					)
 
 					stock_value_diff = (
-						flt(d.base_net_amount)
-						+ flt(d.item_tax_amount / self.conversion_rate)
-						+ flt(d.landed_cost_voucher_amount)
+						flt(d.base_net_amount) + flt(d.item_tax_amount) + flt(d.landed_cost_voucher_amount)
 					)
 				elif warehouse_account.get(d.warehouse):
 					stock_value_diff = get_stock_value_difference(self.name, d.name, d.warehouse)