Move remaining postgres vesion-specific upgrade notes

Move the notes from the Omnibus doc to the respective version-specific
pages.

doc/update/versions/gitlab_14_changes.md

@@ -843,6 +843,10 @@ Other issues:
 
 ### Linux package installations
 
+- The binaries for PostgreSQL 11 and repmgr have been removed. Before upgrading, you must:
+  1. Ensure the installation is using [PostgreSQL 12](https://docs.gitlab.com/omnibus/settings/database.html#upgrade-packaged-postgresql-server).
+  1. If using repmgr, [convert to using Patroni](../../administration/postgresql/replication_and_failover.md#switching-from-repmgr-to-patroni).
+
 - In GitLab 13.0, `sidekiq-cluster` was enabled by default and the `sidekiq` service ran `sidekiq-cluster` under the hood.
   However, users could control this behavior using `sidekiq['cluster']` setting to run Sidekiq directly instead. Users
   could also run `sidekiq-cluster` separately using the various `sidekiq_cluster[*]` settings available in `gitlab.rb`.
@@ -871,10 +875,6 @@ Other issues:
 
   For more information, see
   [Set up the initial password](https://docs.gitlab.com/omnibus/installation/index.html#set-up-the-initial-password).
-- The binaries for PostgreSQL 11 and repmgr have been removed. Prior to upgrading, administrators of Linux package
-  installations must:
-  1. Ensure the installation is using [PostgreSQL 12](https://docs.gitlab.com/omnibus/settings/database.html#upgrade-packaged-postgresql-server).
-  1. If using repmgr, [convert to using Patroni](../../administration/postgresql/replication_and_failover.md#switching-from-repmgr-to-patroni).
 - Two configuration options for Redis were deprecated in GitLab 13 and removed in GitLab 14:
 
   - `redis_slave_role` is replaced with `redis_replica_role`.

doc/update/versions/gitlab_15_changes.md

@@ -790,7 +790,18 @@ A [license caching issue](https://gitlab.com/gitlab-org/gitlab/-/issues/376706)
     for Omnibus GitLab. This replaces `gitlab_shell['custom_hooks_dir']`.
 - PostgreSQL 13.6 is being shipped as the default version for fresh installs and
   12.10 for upgrades. You can manually upgrade to PostgreSQL 13.6 following the
-  [upgrade docs](https://docs.gitlab.com/omnibus/settings/database.html#gitlab-150-and-later).
+  [upgrade docs](https://docs.gitlab.com/omnibus/settings/database.html#upgrade-packaged-postgresql-server) with:
+
+  ```shell
+  sudo gitlab-ctl pg-upgrade -V 13
+  ```
+
+  Until PostgreSQL 12 is removed, you may
+  [pin the PostgreSQL version](https://docs.gitlab.com/omnibus/settings/database.html#pin-the-packaged-postgresql-version-fresh-installs-only)
+  if needed for compatibility or test environment reasons.
+
+  [Fault tolerant and Geo installations require additional steps and planning](../../administration/postgresql/replication_and_failover.md#upgrading-postgresql-major-version-in-a-patroni-cluster).
+
   Because of underlying structural changes, the running PostgreSQL process
   **_must_** be restarted when it is upgraded before running database
   migrations. If automatic restart is skipped, you must run the following

doc/update/versions/gitlab_16_changes.md

@@ -182,6 +182,17 @@ Specific information applies to installations using Geo:
 
 Specific information applies to Linux package installations:
 
+- As of GitLab 16.2, PostgreSQL 13.11 and 14.8 are both shipped with the Linux package.
+  During a package upgrade, the database isn't upgraded to PostgreSQL 14. If you
+  want to upgrade to PostgreSQL 14, you must do it manually:
+
+  ```shell
+  sudo gitlab-ctl pg-upgrade -V 14
+  ```
+
+  PostgreSQL 14 isn't supported on Geo deployments and is [planned](https://gitlab.com/groups/gitlab-org/-/epics/9065)
+  for future releases.
+
 - In 16.2, we are upgrading Redis from 6.2.11 to 7.0.12. This upgrade is expected to be fully backwards compatible.
 
   Redis is not automatically restarted as part of `gitlab-ctl reconfigure`.