[Backport 2.x] Add release notes for 2.19.1 (#5139)

Signed-off-by: Craig Perkins <cwperx@amazon.com>
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Craig Perkins <cwperx@amazon.com>

Author: 3 people

release-notes/opensearch-security.release-notes-2.19.1.0.md

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+## Version 2.19.1 Release Notes
+
+Compatible with OpenSearch and OpenSearch Dashboards version 2.19.1
+
+### Bug Fixes
+* Fix ssl hot reload settings ([#5117](https://github.com/opensearch-project/security/pull/5117))