fix changelog for unreleased SDK hang fix (#5298)

Author: adinauer

CHANGELOG.md

@@ -1,13 +1,18 @@
 # Changelog
 
-## 8.39.0
+## Unreleased
 
 ### Fixes
 
 - Fix `JsonObjectReader` and `MapObjectReader` hanging indefinitely when deserialization errors leave the reader in an inconsistent state ([#5293](https://github.com/getsentry/sentry-java/pull/5293))
   - Failed collection values are now skipped so parsing can continue
   - Skipped collection values emit `WARNING` logs
   - Unknown-key failures and unrecoverable recovery failures emit `ERROR` logs
+
+## 8.39.0
+
+### Fixes
+
 - Fix ANR caused by `GestureDetectorCompat` Handler/MessageQueue lock contention in `SentryWindowCallback` ([#5138](https://github.com/getsentry/sentry-java/pull/5138))
 
 ### Internal