Add Fleet & Agent 8.9.1 release notes (#403)

* Add Fleet & Agent 8.9.1 release notes

* Add notes based on BC1

(cherry picked from commit 6428831)

docs/en/ingest-management/release-notes/release-notes-8.9.asciidoc

@@ -14,13 +14,42 @@
 
 This section summarizes the changes in each release.
 
+* <<release-notes-8.9.1>>
 * <<release-notes-8.9.0>>
 
 Also see:
 
 * {kibana-ref}/release-notes.html[{kib} release notes]
 * {beats-ref}/release-notes.html[{beats} release notes]
 
+// begin 8.9.1 relnotes
+
+[[release-notes-8.9.1]]
+== {fleet} and {agent} 8.9.1
+
+Review important information about the {fleet} and {agent} 8.9.1 release.
+
+[discrete]
+[[security-updates-8.9.1]]
+=== Security updates
+
+{agent}::
+* Updated Go version to 1.19.12. {agent-pull}3186[#3186] 
+
+[discrete]
+[[bug-fixes-8.9.1]]
+=== Bug fixes
+
+{fleet}::
+* Fixes for query error on Agents list in the UI. ({kibana-pull}162816[#162816])
+* Remove duplicate path being pushed to package archive. ({kibana-pull}162724[#162724])
+
+{agent}::
+* Improve two unclear error messages in the Upgrade Watcher {agent-pull}3093[#3093]
+* Add default UTC timezone to synthetics agent Docker images to prevent navigation errors {agent-pull}3160[#3160] {beats-issue}36117[#36117]
+
+// end 8.9.1 relnotes
+
 // begin 8.9.0 relnotes
 
 [[release-notes-8.9.0]]