[baremetal] Drop useless reboot task

It is not used for quite a time.
Some ancient Kolla Ansible used to update host kernel.

Change-Id: I9cdc1ec47ad802b4d65a7b6438a335fc14639e05

ansible/roles/baremetal/tasks/post-install.yml

@@ -229,10 +229,3 @@
   when:
     - change_selinux | bool
     - ansible_os_family == "RedHat"
-
-- name: Reboot
-  command: reboot -f
-  become: True
-  when:
-    - reboot_required is defined
-    - reboot_required | bool