Disable consolidated object storage in config in tests

What does this merge request do and why?

Previously if consolidated object storage were configured, then tests would fail since they would attempt to use the development settings. Disable this in tests so that tests continue to function even when development is configured for object storage.

This mirrors the change in gitlab!147724 (merged).

How to set up and validate locally

1. In your GDK, enable object storage: https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/howto/object_storage.md?ref_type=heads
2. Attempt to run: bundle exec rspec ./spec/services/design_management/save_designs_service_spec.rb

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.