[DOCS] Fix "What's new?" heading level

Think this got messed up by automation

Author: leemthompo

docs/reference/release-notes/highlights.asciidoc

@@ -1,8 +1,6 @@
+[chapter]
 [[release-highlights]]
-== What's new in {minor-version}
-
-coming::[{minor-version}]
-
+= What's new in {minor-version}
 Here are the highlights of what's new and improved in {es} {minor-version}!
 ifeval::["{release-state}"!="unreleased"]
 For detailed information about this release, see the <<es-release-notes>> and