fixed changelog format;

Signed-off-by: Ethern Su <ehaprime@gmail.com>

CHANGELOG.md

@@ -9,8 +9,7 @@ NOTE: As semantic versioning states all 0.y.z releases can contain breaking chan
 We use *breaking :warning:* to mark changes that are not backward compatible (relates only to v0.y.z releases.)
 
 ## Unreleased
-- [#4532]https://github.com/thanos-io/thanos/pull/4532 Mixin: Fixed "all jobs" selector in thanos mixin dashboards
-
+- [#4532](https://github.com/thanos-io/thanos/pull/4532) Mixin: Fixed "all jobs" selector in thanos mixin dashboards
 
 ### Added
 - [#4453](https://github.com/thanos-io/thanos/pull/4453) Tools: Add flag `--selector.relabel-config-file` / `--selector.relabel-config` / `--max-time` / `--min-time` to filter served blocks.