Update CHANGELOG.md

Co-authored-by: Marco Pracucci <marco@pracucci.com>

CHANGELOG.md

@@ -35,7 +35,7 @@ We use *breaking* word for marking changes that are not backward compatible (rel
 
 - [#2671](https://github.com/thanos-io/thanos/pull/2671) Tools: bucket replicate now allows passing repeated `--compaction` and `--resolution` flags.
 - [#2657](https://github.com/thanos-io/thanos/pull/2657) Querier: Now, has the ability to perform concurrent select request per query.
-- [#2752](https://github.com/thanos-io/thanos/pull/2752) Compact: add flag to configure metadata sync interval for the bucket ui
+- [#2752](https://github.com/thanos-io/thanos/pull/2752) Compact: add flag `--block-viewer.global.sync-block-interval` to configure metadata sync interval for the bucket UI.
 
 ## [v0.13.0](https://github.com/thanos-io/thanos/releases) - IN PROGRESS