Update release notes

Author: itsmeichigo

RELEASE-NOTES.txt

@@ -4,6 +4,7 @@
 23.0
 -----
 - [*] Shipping Labels: Made HS tariff number field required in customs form for EU destinations [https://github.com/woocommerce/woocommerce-ios/pull/15946]
+- [*] Order Details: Attempt to improve performance by using a simplified version of product objects. [https://github.com/woocommerce/woocommerce-ios/pull/15959]
 
 22.9
 -----