Remove step that force disable `kube_basic_auth`.

The referenced issue (https://github.com/kubernetes/kubeadm/issues/441) has already been fixed.

roles/kubernetes/master/tasks/main.yml

@@ -3,12 +3,6 @@
   tags:
     - k8s-pre-upgrade
 
-# upstream bug: https://github.com/kubernetes/kubeadm/issues/441
-- name: Disable kube_basic_auth until kubeadm/441 is fixed
-  set_fact:
-    kube_basic_auth: false
-  when: kubeadm_enabled|bool|default(false)
-
 - import_tasks: users-file.yml
   when: kube_basic_auth|default(true)