[DOCS] Fix docs build break from 8.6 RN link (#91619)

Fixes

```

09:43:34 INFO:build_docs:Bad cross-document links: 09:43:34
INFO:build_docs: 
/tmp/docsbuild/target_repo/html/en/elasticsearch/reference/master/release-highlights.html
contains broken links to: 09:43:34 INFO:build_docs:   -
en/elasticsearch/reference/8.6/release-highlights.html

```

docs/reference/release-notes/highlights.asciidoc

@@ -12,8 +12,8 @@ endif::[]
 // Add previous release to the list
 Other versions:
 
-{ref-bare}/8.6/release-highlights.html[8.6]
-| {ref-bare}/8.5/release-highlights.html[8.5]
+//{ref-bare}/8.6/release-highlights.html[8.6]
+{ref-bare}/8.5/release-highlights.html[8.5]
 | {ref-bare}/8.4/release-highlights.html[8.4]
 | {ref-bare}/8.3/release-highlights.html[8.3]
 | {ref-bare}/8.2/release-highlights.html[8.2]