Update Changelog to cover certificate updates

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog b/ChangeLog
index 67b72fc..c977a68 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -26,6 +26,10 @@
    * Fix a compilation error on some platforms when including mbedtls/ssl.h
      with all TLS support disabled. Fixes #6628.
 
+Changes
+   * Update test data to avoid failures of unit tests after 2023-08-07, and
+     update expiring certififcates in the certs module.
+
 = Mbed TLS 2.28.3 branch released 2023-03-28
 
 Features