Remove seat check validation for cloud licenses

Problem

There is currently a seat check in place for activating a cloud license when true-ups are present: https://gitlab.com/gitlab-org/gitlab/-/blob/9d97c3c6dea8569b4a05ed510811a6dc0a699357/ee/app/models/license.rb#L511

This can result in customers being blocked from accessing their purchased self-managed subscriptions.

Proposal

Remove the seat check validation for cloud licenses (whether true-ups are present or not).

Result

A customer can access a self-managed subscription with cloud licensing without any current user check occurring.