update 2.8.0 release notes

Signed-off-by: Kaituo Li <[email protected]>

Author: kaituo

release-notes/opensearch-anomaly-detection-dashboards.release-notes-2.8.0.0.md

@@ -5,3 +5,7 @@ Compatible with OpenSearch Dashboards 2.8.0
 ### Bug Fixes
 
 * fixing test to pass with node 18 ([#491](https://github.com/opensearch-project/anomaly-detection-dashboards-plugin/pull/491))
+
+### Documentation
+
+* Updating maintainers and code owners ([#476](https://github.com/opensearch-project/anomaly-detection-dashboards-plugin/pull/476))