Add 2.9 release notes (#723) (#725)

Signed-off-by: Kavitha Conjeevaram Mohan <[email protected]>
(cherry picked from commit 79a385b)

Co-authored-by: Kavitha Conjeevaram Mohan <[email protected]>

Author: opensearch-trigger-bot[bot]

release-notes/opensearch-reporting.release-notes-2.9.0.0.md

@@ -0,0 +1,9 @@
+## Version 2.9.0.0 Release Notes
+
+Compatible with OpenSearch 2.9.0
+
+### Bug Fixes
+* Removing guava dependency to fix jarhell ([#709](https://github.com/opensearch-project/reporting/pull/709))
+
+### Maintenance
+* Increment version to 2.9.0-SNAPSHOT ([#712](https://github.com/opensearch-project/reporting/pull/712))