Fix Geo check to avoid errors when Geo database doesn't exist

What does this merge request do and why?

This MR fixes the Geo diagnostic check to prevent failures when a Geo database doesn't exist to ensure it only suggests enabling Geo features if necessary, without failing for non-Geo GDK.

How to set up and validate locally

Without Geo enabled or a Geo database setup, Run gdk doctor. The Geo diagnostic check fails with these outputs:

Geo
================================================================================
GDK could be a Geo primary node. However, geo.enabled is not set to true in your gdk.yml.
Update your gdk.yml to set geo.enabled to true.

https://gitlab.com/gitlab-org/gitlab-development-kit/blob/main/doc/howto/geo.md

With this change, not having a Geo database will not cause the Geo diagnostic check to fail.

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.