Requires https://gitlab.com/gitlab-org/gitlab-ce/issues/54318 to be completed first. ## Problem [`else` conditional](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/app/models/clusters/platforms/kubernetes.rb#L84) was added on `Clusters::Platforms::Kubernetes#predefined_variables` to ensure compatibility with those Clusters that do not have `Clusters::KubernetesNamespace` relationship for some reason. After background migration on 11.5 https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22433, we need to remove it, as it might not be necessary ## Proposal