[Observability] 9.2.3 release notes (#4354)

Closes #4343 and adds the 9.2.3 Observability release notes.

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Co-authored-by: florent-leborgne <florent.leborgne@elastic.co>

Author: mdbirnstiehl

release-notes/elastic-observability/index.md

@@ -21,6 +21,19 @@ To check for security updates, go to [Security announcements for the Elastic sta
 % ### Fixes [elastic-observability-next-fixes]
 % *
 
+## 9.2.3 [elastic-observability-9.2.3-release-notes]
+
+### Features and enhancements [elastic-observability-9.2.3-features-enhancements]
+* Adds a message to tell users when a stream is missing [#244366]({{kib-pull}}244366).
+* Adds a warning when deleting API keys that are currently in use by alerting rules [#243353]({{kib-pull}}243353).
+* Shows supported schemas in the Infrastructure inventory [#244481]({{kib-pull}}244481).
+
+
+### Fixes [elastic-observability-9.2.3-fixes]
+* Fixes alias resolution when checking lock index mappings [#244559]({{kib-pull}}244559).
+* Adds managed field to `dataViewSpecSchema` [#244134]({{kib-pull}}244134).
+* Removes mentions of template snippets from descriptions [#243656]({{kib-pull}}243656).
+
 ## 9.2.2 [elastic-observability-9.2.2-release-notes]
 
 ### Features and enhancements [elastic-observability-9.2.2-features-enhancements]