Ensure database.yml includes `gssencmode: disable`

What does this merge request do and why?

Ensure database.yml includes gssencmode: disable

This is required for any PostgreSQL that has been compiled with GSSAPI enabled to prevent segfaults

See: https://github.com/ged/ruby-pg/issues/311

How to set up and validate locally

1. Run gdk reconfigure
2. Ensure your gitlab/config/database.yml includes : gssencmode: disable for every database entry

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.