add changelog

Signed-off-by: Ben Ye <ben.ye@bytedance.com>

CHANGELOG.md

@@ -26,6 +26,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#5224](https://github.com/thanos-io/thanos/pull/5224) Receive: Remove sort on label hashing
 - [#5231](https://github.com/thanos-io/thanos/pull/5231) Tools: Bucket verify tool ignores blocks with deletion markers.
 - [#5244](https://github.com/thanos-io/thanos/pull/5244) Query: Promote negative offset and `@` modifier to stable features as per Prometheus [#10121](https://github.com/prometheus/prometheus/pull/10121).
+- [#5255](https://github.com/thanos-io/thanos/pull/5255) InfoAPI: Set store API unavailable when stores are not ready.
 
 ### Removed