Update release notes

Author: itsmeichigo

RELEASE-NOTES.txt

@@ -5,6 +5,7 @@
 -----
 - [*] 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]
+- [*] Use simple product objects in Shipping Labels and Blaze flows. [https://github.com/woocommerce/woocommerce-ios/pull/15965]
 
 22.9
 -----