update changelog

Author: denrase

CHANGELOG.md

@@ -9,8 +9,8 @@
 - Refrain from overwriting the span status for unfinished spans ([#1577](https://github.com/getsentry/sentry-dart/pull/1577))
   - Older self-hosted sentry instances will drop transactions containing unfinished spans.
     - This change was introduced in [relay/#1690](https://github.com/getsentry/relay/pull/1690) and released with [22.12.0](https://github.com/getsentry/relay/releases/tag/22.12.0)
-  
-## 7.9.0
+
+## Unreleased
 
 ### Fixes