Auto upgrade non-HA PostgreSQL to PG14

Postgres 14 is going to become our minimum supported version in GitLab 17. We should turn on the auto-upgrade for single node installs in 16.11

• Swap attempt_auto_pg_upgrade? to true in https://gitlab.com/gitlab-org/omnibus-gitlab/-/blob/master/files/gitlab-ctl-commands/upgrade.rb (!7490 (merged))
• Swap ATTEMPT_AUTO_PG_UPGRADE to true in https://gitlab.com/gitlab-org/omnibus-gitlab/-/blob/master/docker/assets/wrapper (!7490 (merged))
• Ensure the pg-upgrade upgrade command is working as expected (!7490 (comment 1821976571))
• Update the documentation to reflect these changes. (gitlab!147402 (merged))

The last time we did this was #7392 (closed)