Add ci-bot to list of approved users for automerge (#5186)

Signed-off-by: Sayali Gaikawad <gaiksaya@amazon.com>

Author: gaiksaya

.github/workflows/automatic-merges.yml

@@ -33,6 +33,7 @@ jobs:
           allowed-authors: |
             dependabot
             opensearch-trigger-bot
+            opensearch-ci-bot
             peterzhuamazon
             gaiksaya
             rishabh6788