Link to upgrade notes explictly

- Add explicit link to upgrade notes

Signed-off-by: Robert Marshall <rmarshall@gitlab.com>

doc/package-information/postgresql_versions.md

@@ -15,7 +15,7 @@ Read more about update policies and warnings in the PostgreSQL
 | GitLab version | PostgreSQL versions | Default version for fresh installs | Default version for upgrades | Notes |
 | -------------- | --------------------- | ---------------------------------- | ---------------------------- | ----- |
-| 13.6 | 11.9, 12.4 | 12.4 | 11.9 | For upgrades users can manually upgrade to 12.4 following the upgrade docs. |
+| 13.6 | 11.9, 12.4 | 12.4 | 11.9 | For upgrades users can manually upgrade to 12.4 following the [upgrade docs](../settings/database.html#gitlab-133-and-later). |
 | 13.4 | 11.9, 12.4 | 11.9 | 11.9 | Package upgrades aborted if users not running PostgreSQL 11 already |
 | 13.3 | 11.7, 12.3 | 11.7 | 11.7 | Package upgrades aborted if users not running PostgreSQL 11 already |
 | 13.0 | 11.7 | 11.7 | 11.7 | Package upgrades aborted if users not running PostgreSQL 11 already |