update CHANGELOG

CHANGELOG.md

@@ -20,7 +20,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#4680](https://github.com/thanos-io/thanos/pull/4680) Query: add `exemplar.partial-response` flag to control partial response.
 - [#4679](https://github.com/thanos-io/thanos/pull/4679) Added `enable-feature` flag to enable negative offsets and @ modifier, similar to Prometheus.
 - [#4696](https://github.com/thanos-io/thanos/pull/4696) Query: add cache name to tracing spans.
-- [#4764](https://github.com/thanos-io/thanos/pull/4764) Compactor: add block-viewer.global.sync-block-timeout for sync block metas
+- [#4764](https://github.com/thanos-io/thanos/pull/4764) Compactor: add `block-viewer.global.sync-block-timeout` flag to set timeout of syncing block metas
 
 ### Fixed