Add known-issue docs for index/alias name clash bug

Relates elastic#91456
Relates elastic#91887

docs/reference/release-notes/8.5.0.asciidoc

@@ -328,3 +328,10 @@ Packaging::
 * When using date range search with format that does not have all date fields (missing month or day)
 an incorrectly parsed date could be used. The workaround is to use date pattern with all date fields (year, month, day)
 (issue: {es-issue}90187[#90187])
+
+* It is possible to inadvertently create an alias with the same name as an
+index in version 8.5.0. This action leaves the cluster in an invalid state in
+which several features will not work correctly, and it may not even be possible
+to restart nodes while in this state. Upgrade to 8.5.1 as soon as possible to
+avoid the risk of this occurring ({es-pull}91456[#91456]). If your cluster is
+affected by this issue, upgrade to 8.5.3 to repair it ({es-pull}91887[#91887]).