nfs: remove legacy task

This fact is never used, let's remove the task.
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

roles/ceph-nfs/tasks/create_rgw_nfs_user.yml

 ---
-- name: set_fact container_exec_cmd_nfs
-  set_fact:
-    container_exec_cmd_nfs: "{{ container_binary }} exec ceph-mon-{{ hostvars[groups[mon_group_name][0]]['ansible_facts']['hostname'] }}"
-  when: containerized_deployment | bool
-
 - name: create rgw nfs user "{{ ceph_nfs_rgw_user }}"
   radosgw_user:
     name: "{{ ceph_nfs_rgw_user }}"