Remove Customer argument from namespace eligibility resolver
Problem
In https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/12004 and https://gitlab.com/gitlab-org/customers-gitlab-com/-/merge_requests/12343 we removed behavior dependent on the customer argument in Gitlab::Namespace.wrap_collection. Since it's no longer needed, we can remove it from callers and the method signature.