Remove require_organization Feature Flag

What does this MR do and why?

This MR removes the require_organization feature flag. The flag is now enabled and can be removed.

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

• Part of #466141

MR acceptance checklist

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

How to set up and validate locally

We can validate this change by creating a Group, using GDK:

• Create a group http://127.0.0.1:3000/groups/new : the group should be created.

Related to #470839