add new changelog headers

Author: Kristófer R

changelog.txt

@@ -1,5 +1,7 @@
 *** Changelog ***
 
+= x.x.x - 2023-xx-xx =
+
 = 7.1.0 - 2023-02-08 =
 * Fix - Replace some post meta methods with equivalent methods compatible with HPOS.
 * Fix - Rare cases of payment processing failing when webhooks arrive before customer is redirected when UPE is enabled will no longer occur.

readme.txt

@@ -128,10 +128,7 @@ If you get stuck, you can ask for help in the Plugin Forum.
 
 == Changelog ==
 
-= 7.1.0 - 2023-02-08 =
-* Fix - Replace some post meta methods with equivalent methods compatible with HPOS.
-* Tweak - Update minimum supported versions for WordPress, WooCommerce, and PHP.
-* Update – Declare this plugin compatible with High-Performance Order Storage (HPOS).
+= x.x.x - 2023-xx-xx =
 
 
 [See changelog for all versions](https://raw.githubusercontent.com/woocommerce/woocommerce-gateway-stripe/trunk/changelog.txt).