Move delayed delete GroupFinder code to CE

What does this MR do and why?

Due to a recent data-loss incident, the decision was made to down-tier delayed deletion. This MR moves delayed deletion related finder filters from EE to CE. The only functionality change is removing a license check, which is covered by specs.

References

#535263 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the feature flag (needed to mark free projects for deletion)

   Feature.enable(:downtier_delayed_deletion)

2. Delete a project in a group

3. Verify that the finders work, replace the marked_for_deletion_on with the correct date.

   GroupsFinder.new(User.first, { marked_for_deletion_on: '2025-04-10' }).execute

4. Run the rails console in FOSS mode (FOSS_ONLY=1 rails c) and verify the finders still work.

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #535263 (closed)