Merge pull request #18067 from cockroachdb/update_release_notes

Added note to v23.1.12 release notes

src/current/_includes/releases/v23.1/v23.1.12.md

@@ -1,5 +1,11 @@
 ## v23.1.12
 
+{{ site.data.alerts.callout_info }}
+v23.1.12 is currently available only on select CockroachDB {{ site.data.products.dedicated }} clusters. If you wish to upgrade your {{ site.data.products.dedicated }} cluster to v23.1.12, please submit a [support request](https://support.cockroachlabs.com/hc/en-us/requests/new).
+
+This release is currently not available for CockroachDB {{ site.data.products.serverless }} or {{ site.data.products.core }} customers.
+{{ site.data.alerts.end }}
+
 Release Date: November 13, 2023
 
 {% comment %}{% include releases/release-downloads-docker-image.md release=include.release %}{% endcomment %}