update: moved release notes to v21.8

Author: pmusolino

RELEASE-NOTES.txt

@@ -11,11 +11,11 @@
 - [*] Background image upload: Fix missing error notice in iPhones [https://github.com/woocommerce/woocommerce-ios/pull/15117]
 - [*] Background image upload: Show a notice when the user leaves product details while uploads are pending [https://github.com/woocommerce/woocommerce-ios/pull/15134]
 - [*] Filters applied in product selector no longer affect the main product list screen. [https://github.com/woocommerce/woocommerce-ios/pull/14764]
+- [*] Better error messages if Application Password login is disabled on user's website. [https://github.com/woocommerce/woocommerce-ios/pull/15031]
 
 21.7
 -----
 - [**] Fixed an issue with the WordPress Media Library not loading due to a decoding error in media details sizes. [https://github.com/woocommerce/woocommerce-ios/pull/15056]
-- [*] Better error messages if Application Password login is disabled on user's website. [https://github.com/woocommerce/woocommerce-ios/pull/15031]
 - [*] Now, usernames and emails in text fields across multiple login views are no longer capitalized. [https://github.com/woocommerce/woocommerce-ios/pull/15002]
 - [*] Product Details: Display cover tag on the first product image [https://github.com/woocommerce/woocommerce-ios/pull/15041]
 - [*] Payments: Update learn more links to open Stripe-specific docs when using that gateway [https://github.com/woocommerce/woocommerce-ios/pull/15035]