Add features upgrade known issue to 8.14.3 (#111618)

Author: thecoop

docs/reference/release-notes/8.14.3.asciidoc

@@ -3,6 +3,16 @@
 
 Also see <<breaking-changes-8.14,Breaking changes in 8.14>>.
 
+[[known-issues-8.14.3]]
+[float]
+=== Known issues
+* When upgrading clusters from version 8.11.4 or earlier, if your cluster contains non-master-eligible nodes,
+information about the new functionality of these upgraded nodes may not be registered properly with the master node.
+This can lead to some new functionality added since 8.12.0 not being accessible on the upgraded cluster.
+If your cluster is running on ECK 2.12.1 and above, this may cause problems with finalizing the upgrade.
+To resolve this issue, perform a rolling restart on the non-master-eligible nodes once all Elasticsearch nodes
+are upgraded. This issue is fixed in 8.15.0.
+
 [[bug-8.14.3]]
 [float]
 === Bug fixes