[DOCS] Update upgrade docs for 7.15

Author: jrodewig

docs/reference/release-notes/highlights.asciidoc

@@ -8,7 +8,8 @@ For detailed information about this release, see the <<es-release-notes>> and
 
 // Add previous release to the list
 Other versions:
-{ref-bare}/7.13/release-highlights.html[7.13]
+{ref-bare}/7.14/release-highlights.html[7.14]
+| {ref-bare}/7.13/release-highlights.html[7.13]
 | {ref-bare}/7.11/release-highlights.html[7.12]
 | {ref-bare}/7.11/release-highlights.html[7.11]
 | {ref-bare}/7.10/release-highlights.html[7.10]

docs/reference/upgrade.asciidoc

@@ -37,7 +37,7 @@ ifeval::[ "{version}" != "{minor-version}.0" ]
 |<<rolling-upgrades,Rolling upgrade>> to {version}
 endif::[]
 
-|7.0–7.13
+|7.0–7.14
 |<<rolling-upgrades,Rolling upgrade>> to {version}
 
 |6.8