Docs feedback: Upgrade to 16.0 fails citing gitaly['gitconfig'] when omnibus_gitconfig['system'] is defined

Problem to solve

• What product or feature(s) affected? Upgrade from GitLab v15.10-11 to v16.
• What docs or doc section affected? Upgrading GitLab - Gitaly: Omnibus GitLab configuration structure change
• Is there a problem with a specific document, or a feature/process that's not addressed sufficiently in docs? Yes, upgrade fails with somewhat misleading error.
• Any other ideas or requests?

Further details

When omnibus_gitconfig['system'] has options in config.rb, the upgrade will fail stating gitaly['gitconfig'] has been deprecated since 15.10 and was removed in 16.0. In GitLab 15.10, Gitaly's configuration in Omnibus GitLab was changed to structurally match Gitaly's own configuration. Please see the migration instructions at https://docs.gitlab.com/ee/update/#15100. This still occurs when there are no references to gitaly in gitlab.rb.

Proposal

Consider improving the deprecation warning to mention the omnibus_gitconfig section.

Update the config.rb template to remove the omnibus_gitconfig example.

Who can address the issue

Other links/references

• Upgrading GitLab - Gitaly: Omnibus GitLab configuration structure change
• r/gitlab: Upgrade to Gitlab 16.0.1 complains about Gitaly despite being disabled: Someone else is experiencing the issue.

Link the doc and describe what is wrong with it.