Default "Groups and projects" page display to "Groups"

Background

Follow-up from #505071 (comment 2333188693)

Proposal

Currently the organization_groups_projects_display column on the user_preferences table defaults to 0 (which is projects) - https://gitlab.com/gitlab-org/gitlab/-/blob/master/db/migrate/20240527073021_add_organization_groups_projects_display.rb#L7

From a UX perspective it would be better if it defaulted to 1 (which is groups). We should create a new migration to change the default to 1.

Implementation guide

1. Create a new migration that changes the default from 0 to 1. See https://docs.gitlab.com/development/migration_style_guide/#changing-default-value-for-a-column
2. Update affected test in spec/helpers/organizations/organization_helper_spec.rb and spec/models/user_preference_spec.rb