Remove outdated comment

bootstrap-os does not do anything in sudoers since e2ad6aad5 (bootstrap:
rework role (#4045), 2019-02-11).

So SSH pipelining working is effectively a pre-requisite anyway.

playbooks/facts.yml

@@ -5,10 +5,6 @@
   any_errors_fatal: "{{ any_errors_fatal | default(true) }}"
   gather_facts: false
   environment: "{{ proxy_disable_env }}"
-  vars:
-    # Need to disable pipelining for bootstrap-os as some systems have requiretty in sudoers set, which makes pipelining
-    # fail. bootstrap-os fixes this on these systems, so in later plays it can be enabled.
-    ansible_ssh_pipelining: false
   roles:
     - { role: bootstrap-os, tags: bootstrap-os}
     - { role: kubespray-defaults }