Re-add link to 8.7 release highlights (#93758)

* Re-add link to 8.7 release highlights

* Rebuild

---------

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>

docs/reference/release-notes/highlights.asciidoc

@@ -12,7 +12,8 @@ endif::[]
 // Add previous release to the list
 Other versions:
 
-{ref-bare}/8.6/release-highlights.html[8.6]
+{ref-bare}/8.7/release-highlights.html[8.7]
+| {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]